Respuesta :
First of all, we can simply find the answer, if we pay attention to what the question is asking. It's asking for a STRUCTURAL adaptation, which means the adaptation we search for needs to involve a change in structure.
Nor A, B or C represent a change in structure, but B does. It shows us a change in the structure of tree seeds, which has helped them during reproduction.
Hope it helped,
BioTeacher101