What is artificial selection? A. When a new allele is formed by mutation
B. When humans breed an animal for a certain trait
C. When extreme traits are selected by nature
D. When 60 percent of a species dies at one time

The answer is B since that's the definition of artificial selection ,selective breeding made by humans

the principles and empirical processes of discovery and demonstration considered characteristic of or necessary for scientific investigation, generally involving the observation of phenomena, the formulation of a hypothesis concerning the phenomena, experimentation to test the hypothesis, and development of a conclusion that confirms, rejects, or modifies the hypothesis.