An Experiment Found That Newborn Rats Who Were Genetically Predisposed

Multiple Choice

An experiment found that newborn rats who were genetically predisposed to be skittish, nervous, and high-strung would develop into calm, exploratory, and stress-resistant adult rats when raised by genetically unrelated, attentive mothers. The researchers concluded that:

A) although the rats' DNA did not change, the chemicals that controlled their gene expression did change.
B) the genes controlling the rats' behavior must have mutated.
C) although the rats' DNA changed, the chemicals that controlled their gene expression did not.
D) the epigenetic changes were inherited from the previous generation of temperamental rats and were only expressed when the environment was favorable.