Answer:
A. selective breeding.
Step-by-step explanation:
Selective breeding, also known as artificial selection, is the process of breeding plants and animals for specific desirable traits. In the case of Farmer Joe, he is selecting the cows that produce the most milk and only allowing them to reproduce. By doing this, he is increasing the frequency of the genes responsible for high milk production in his herd. Over time, this results in a population of cows with a higher average milk production than the original population. Selective breeding has been used for thousands of years by humans to improve the quality of crops and livestock. This process has led to the development of many of the plant and animal species that we rely on today.