Which of these is an example of selective breeding?

Question

A Mold is grown in a lab and used to make medicines.
B Sheep are cloned to produce more of the same type of sheep.
C Genes are inserted into bacteria to make many copies of the gene for a certain trait
D Hens that lay the most eggs are crossed with healthy roosters to produce many healthy offspring.

Answer 1

D Hens that lay the most eggs are crossed with healthy roosters to produce many healthy offspring.