Answer:
A. The children will be more likely to survive than if they did not have the trait.
Explanation:
Process of elimination
B. It will not affect the children.
Cannot be true, if it didn't impact the children then how would survival of the fittest work?
D. The children will be able to adapt if the environment changes.
That just... not how adapting works when it comes to evolution.
C. The children will be more likely to survive than their parents were
Everyone has the same trait, everyone is equal in that regard.
A. The children will be more likely to survive than if they did not have the trait.
"Suppose a pair of animals has a trait that helps them survive in their environment." The trait helps them survive. Not having the trait makes them less likely to survive. A is correct