Question

are studying the shape, size, and parts of the heart. they are studying the

anatomy

chemistry

physiology

Explanation:

Anatomy is the study of the structure of the body and its parts. Studying the shape, size, and parts of the heart falls under anatomy. Chemistry is about the composition, structure, properties and reactions of matter. Physiology is the study of the functions of the body and its parts. Since the focus is on structure here, it's anatomy.

Answer:

A. anatomy