Answer:
The actual answer is C.
Step-by-step explanation:
From Odyssey: "There are internal and external environmental influences regarding if and how genes are expressed. For an internal example, have you ever noticed that most male birds are more brightly colored than female birds? This is because chemicals only in the males control whether the gene for bright colors is expressed. An example of an external influence is a person who stays out of the sun because they know that they are at risk for developing a deadly type of skin cancer, and their behavior may keep them from getting the cancer."