What is the function of the structure labeled A?

It pumps blood over the internal organs.

It aids in crawling, digging, and feeding.

It forms the outer wall of the animal's body.

It delivers oxygen to the blood.

Answer is present in the explanation.

Explanation:

If the labeled A has structure of heart so we can say that it pumps blood to all the internal organs of the body. If the labeled A shows the structure of foot of any organism so we can say that it aids in crawling, digging in the soil and capturing the food for itself. If the labeled A indicates the structure of epithelial tissue so we can say that it forms the outer wall of the animal's body. If the labeled A shows the structure of hemoglobin cell so we can choose that it delivers oxygen to the blood.