Final answer:
The opposite of posterior is anterior (Option B), which describes the front or direction toward the front of the body in anatomical terms.
Step-by-step explanation:
The opposite of posterior is anterior. In anatomical terminology, posterior (or dorsal) describes the back or direction toward the back of the body. Conversely, anterior (or ventral) describes the front or direction toward the front of the body. This terminology is essential for accurately describing the relative locations of body structures in the field of anatomy, a science that studies the form and composition of the body's structures. When referring to the body's main cavities, the dorsal body cavity is also known as the posterior cavity, while the ventral body cavity is referred to as the anterior cavity. Therefore, the correct answer is B. anterior.