3. If a species of bird flies fast to escape predators, then over time (many, many generations) the wing muscles of that species will get stronger so that it can fly faster. How does this happen?
A. Birds born with stronger wing muscles survive longer and pass down that trait to their offspring.
B. The more a bird flies, the stronger it gets and passes down that trait to its offspring.
C. The more a bird flies, the more fatigued it gets, and it passes down that trait to its offspring.
D. Birds born with weaker wing muscles survive longer and pass down that trait to their offspring.