Which of the Following Statements Best Describes a Trigger

Which of the following statements best describes a trigger?

A) It is a computer program stored within a database that runs to keep the database consistent when certain conditions arise.
B) It is a computer program stored in a database that is used to enforce business rules.
C) It is a set of inherent procedures in an ERP solution that implement standard business processes.
D) It is a programming paradigm that describes computation in terms of statements that change a program state.