Question 1

When a program creates a derived-class object,the Object constructor is the last constructor called and the first whose body finishes executing.

Accepted Answer

This statement is true. When a program creates a derived-class object, the derived class constructor is called first, then the base class constructor and finally the object constructor. The object constructor is the last constructor called and the first whose body finishes executing.

Question 2

Polymorphism allows for specifics to be dealt with during:
A)execution
B)compilation
C)programming
D)debugging

Accepted Answer

Polymorphism allows for specific method implementations to be determined during execution based on the actual object type, rather than at compile time. Therefore, the correct choice is execution.

Question 3

How can a derived class constructor ccall a base class constructor?
A)implicitly
B)explicitly
C)a and b
D)the derived class cannot call the base class constructor

Accepted Answer

A derived class constructor can call a base class constructor both implicitly and explicitly. Implicitly, the base class's default constructor is called if no constructor is specified. Explicitly, a derived class can call a specific base class constructor using an initializer list.

Question 4

For which of the following would polymorphism not provide a clean solution?
A)A billing program where there is a variety of clients who are billed with different fee structures.
B)A maintenance log program where a variety of machine data is collected and maintenance schedules are produced for each machine based on the data collected.
C)A program to compute a 5% savings account interest for bank clients.
D)An IRS program that maintains information on a variety of taxpayers and determines who to audit based on criteria for classes of taxpayers.

Accepted Answer

Polymorphism would not provide a clean solution for a program to compute a fixed savings account interest for bank clients since there is no variation in the interest calculation based on the type or characteristics of the account holder.

Question 5

In practice,derived classes should depend only on the base-class services (that is,Private methods and properties)and not on the base-class data implementation.

Accepted Answer

In practice,derived classes should depend only on the base-class services (that is,non-Private methods and properties)and not on the base-class data implementation.

Question 6

To call the base-class default constructor explicitly,the call to a base-class constructor must be the first statement in the derived-class-constructor definition.

Accepted Answer

When you call an Overridable base class method on a derived class object,the derived class version of the method executes.This is the basis of polymorphism.

Question 7

Which statement is true when a base class has Protected instance variables?
A)A derived class object can assign an invalid value to the base class's Protected instance variables.
B)Derived class methods can depend on the base class's Protected data implementation.
C)Derived classes would need to be modified if the base class's Protected data implementation changes.
D)All of the above.

Accepted Answer

The answer of Which statement is true when a base...

Question 8

When a derived-class member overrides a base-class member,the base-class member can be accessed from the derived-class by using the Visual Basic keyword .
A)MyBase
B)Top
C)Super
D)None of the above

Accepted Answer

The keyword "MyBase" is used in Visual Basic to access the base-class member from a derived-class member that overrides it. This allows the derived-class member to call the original implementation of the base-class member if it needs to, while still being able to add or modify its own functionality. The other options (B and C) are not valid keywords in Visual Basic for accessing the base-class member.

Question 9

When a request is made to use a derived-class-object method through a base-class reference,Visual Basic polymorphically chooses the correct overridden method in the derived class that is associated with the object.

Accepted Answer

This statement accurately describes how polymorphism works in Visual Basic. When a derived-class-object method is called through a base-class reference, the correct overridden method in the derived class is chosen based on the type of object being referenced. This allows for more flexible and dynamic programming, as different types of objects can be treated as if they are the same type, as long as they share a common base class.

Question 10

Polymorphism involves:
A)the same message sent to a variety of objects of types related by inheritance
B)a specific message sent to each specific object
C)different messages sent to one object
D)None of the above.

Accepted Answer

Polymorphism refers to the capability of objects of various classes related through inheritance to respond to the same message. When the same message is sent to different objects of the same parent class but different child classes, they will respond differently based on their individual implementation of the method. Thus, option A is the correct choice.

Question 11

The first task of any base class's constructor is to call its derived class's constructor.

Accepted Answer

The first task of any derived class's constructor is to call its base class's con?structor.

Question 12

With Protected instance variables in the base class,all the derived classes of the base class may need to be modified if the base-class implementation changes.In such a case,the software is said to be non-modifiable,because a small change in the base class can "break" derived-class implementations.

Accepted Answer

In such a case,the software is said to be brittle.

Question 13

Polymorphism allows the addition of classes providing they were at least considered during program development.

Accepted Answer

Polymorphism can be used to include classes that were not even envisioned during program development.

Question 14

Consider the classes below: 
Which of the statements below is false?
A)Both variables a and b are instance variables.
B)After the constructor for Class B executes,the variable a will have the value 7.
C)After the constructor for Class B executes,the variable b will have the value 8.
D)A reference to an object of Class A can be treated as a reference to an object of Class B.

Accepted Answer

The answer of Consider the classes below: 
Which of the...

Question 15

When a base class method is overridden in a derived class,it is common to have the derived class version call the base class version and then do some additional work.

Accepted Answer

This is a common practice in object-oriented programming known as method overriding with super(). It allows the derived class to inherit and use the functionality of the base class while adding its own unique functionality.

Question 16

Base class methods with this level of access cannot be called from derived classes.
A)Private
B)Public
C)Protected
D)None of the above

Accepted Answer

Private methods can only be accessed within the base class and cannot be called from derived classes.  Protected methods can only be accessed within the base class and derived classes, while public methods can be accessed from anywhere. Therefore, private is the best choice for this statement.

Question 17

A base class's method that's overridden in a derived class will be executed implicitly when the derived class's method is called.

Accepted Answer

Only constructors are executed implicitly in this fashion;a base-class method can be executed explicitly by using the MyBase keyword.

Question 18

The Protected members of a base class may be accessed in their class or any classes derived from that base class.

Accepted Answer

Protected members in a base class are accessible within the class itself and any classes that are derived from it.

Question 19

When a derived class constructor calls its base class constructor,what happens if the base class's constructor does not assign a value to one of its instance variables?
A)a syntax error occurs
B)a compile-time error occurs
C)a run-time error occurs
D)the instance variables are initialized to their default values

Accepted Answer

If the base class's constructor does not explicitly assign a value to an instance variable, then the variable is still initialized to its default value. For example, if the instance variable is an int, it will be initialized to 0. Therefore, there will be no error or issue, and the instance variable will have a valid value.

Question 20

Private fields of a base class can be accessed in a derived class
A)by calling Private methods declared in the base class
B)by calling Public or Protected methods declared in the base class
C)directly
D)All of the above

Accepted Answer

Private fields of a base class cannot be accessed directly in a derived class. They can only be accessed through public or protected methods provided by the base class.

Quiz 10: Object-Oriented Programming: Inheritance

When a program creates a derived-class object,the Object constructor is the last constructor called and the first whose body finishes executing.

Polymorphism allows for specifics to be dealt with during:

How can a derived class constructor ccall a base class constructor?

For which of the following would polymorphism not provide a clean solution?

In practice,derived classes should depend only on the base-class services (that is,Private methods and properties)and not on the base-class data implementation.

To call the base-class default constructor explicitly,the call to a base-class constructor must be the first statement in the derived-class-constructor definition.

Which statement is true when a base class has Protected instance variables?

When a derived-class member overrides a base-class member,the base-class member can be accessed from the derived-class by using the Visual Basic keyword .

When a request is made to use a derived-class-object method through a base-class reference,Visual Basic polymorphically chooses the correct overridden method in the derived class that is associated with the object.

Polymorphism involves:

The first task of any base class's constructor is to call its derived class's constructor.

With Protected instance variables in the base class,all the derived classes of the base class may need to be modified if the base-class implementation changes.In such a case,the software is said to be non-modifiable,because a small change in the base class can "break" derived-class implementations.

Polymorphism allows the addition of classes providing they were at least considered during program development.

Consider the classes below: Which of the statements below is false?

When a base class method is overridden in a derived class,it is common to have the derived class version call the base class version and then do some additional work.

Base class methods with this level of access cannot be called from derived classes.

A base class's method that's overridden in a derived class will be executed implicitly when the derived class's method is called.

The Protected members of a base class may be accessed in their class or any classes derived from that base class.

When a derived class constructor calls its base class constructor,what happens if the base class's constructor does not assign a value to one of its instance variables?

Private fields of a base class can be accessed in a derived class