Answer:
e. cross your flies with flies from another lab.
Step-by-step explanation:
The given small population of flies is exhibiting loss of genetic variations due to small population size leading to reduced viability. The populations with small size often exhibit loss of vigor due to reduced genetic variability. The loss of viability as caused by loss of genetic variations can be overcome by out-crossing. In out-crossing, the related individuals with no common ancestors for at least 5-6 generations are crossed.
Out-crossing increases the genetic variations and thereby, restores the lost viability of the population. Therefore, the population of flies should be allowed to mate with the flies from another lab to increase genetic variations and thereby, the viability of the progeny.