You Are Maintaining a Small Population of Fruit Flies in the Laboratory

You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation.After several generations,you notice the viability of the flies has decreased greatly.Recognizing that small population size is likely to be linked to decreased viability,the best way to reverse this trend is to

A) cross your flies with flies from another lab.
B) reduce the number of flies that you transfer at each generation.
C) transfer only the largest flies.
D) change the temperature at which you rear the flies.
E) shock the flies with a brief treatment of heat or cold to make them more hardy.