Final answer:
The opposite of anterior is posterior. Anterior means the front of the body, while posterior refers to the back. The correct answer to the question is A. Posterior.
Step-by-step explanation:
The opposite of anterior is posterior. In anatomical terminology, anterior or ventral refers to the front or direction toward the front of the body. For example, the toes are considered anterior to the foot. Conversely, posterior or dorsal indicates the back or direction toward the back of the body, such as the popliteus muscle being posterior to the patella.
The anterior and posterior directional terms are used to describe the relative positions of structures within the body. Thus, the correct answer to the student's question is A. Posterior. Other options like exterior, superior, and proximal have different anatomical meanings. For example, superior refers to a position above another part, and proximal indicates nearer to the point of attachment to the trunk.