Final answer:
The term 'posterior' refers to a position towards the back side of the body and is also known as dorsal. It contrasts with 'anterior,' which refers to the front side. An example of a posterior structure is the dorsal cavity that contains the brain and spinal cord.
Step-by-step explanation:
The definition of posterior is related to position and direction within the body. Specifically, something that is posterior is located towards the back side of the body. This term is also known as dorsal. For example, in human anatomy, the posterior or dorsal cavity includes the body cavities that house the brain and spinal cord. An anatomical illustration of this can be seen in a posterior view of the body, where the regions towards the back are labeled. This contrasts with anterior (or ventral), which describes the front or direction toward the front of the body. Thus, the correct answer to the student's question is 2) Relative to the back (back side) of the body.