Which statement correctly describes the position of the structures?
a. the navel is superior to the head.
b. the head is inferior to the abdomen.
c. the heart is anterior to the breastbone.
d. the heart is medial to the arm.

The heart is medial to the arm describes the position of the structures.  Explanation:

Anatomical terminology provides the knowledge of Some useful terms for describing the body structure. These are divided into three groups of terms which are directional terms, planes of the body, and body cavity. The directional terms are used to describe the position of the structure relative to other structure in the body. Medial comes under directional terms. Medial means towards the midline of body. Here the heart is in the middle or medial of the two arms.

This image says it all Mr. Bot