Answer:
The correct answer is "Relationship of structure to function".
Explanation:
In biology, relationship of structure to function is a concept that refers to every structure found in nature (from a molecule to an organ) has its specific form to serve a purpose. This theme is applied to evolution as well, explaining why the modification of an organism’s parts to adapt to its habitat. For instance, the long neck of a giraffe to reach the leaves of the highest trees to feed from them.
