Help Plz!!

Which sentence does not describe a structural adaptation?

A.
An elephant has a long trunk that it uses to reach leaves high in a tree.

B.
A dog walks to a stream and drinks when it gets thirsty.

C.
A hummingbird has a long, thin beak to sip nectar from flowers.

D.
A rosebush has thorns to protect it from animals that might eat it.