Which of the following relates to weight?

The term that relates to weight is "bar/o." This prefix is derived from the Greek word "baros," which means weight. In medical terminology, "barometer" and "barometry" utilize this prefix to describe methods of measuring pressure and weight in various contexts, particularly in relation to atmospheric pressure. This relationship underscores the concept of weight in both physical and medical applications.

On the other hand, "bas/o" refers to a base or base of a structure, "bi/o" is related to life or living organisms, and "auditory" pertains specifically to hearing. These terms do not have any direct connection to the concept of weight, confirming that "bar/o" is indeed the correct choice for this question.