How do volume of distribution and clearance differ?

The correct choice highlights that volume of distribution and clearance serve distinct roles in pharmacokinetics. Volume of distribution is a theoretical concept that describes how extensively a drug disperses throughout the body relative to the concentration of the drug in plasma. It can provide insights into the drug's distribution among body tissues and whether it tends to remain in the bloodstream or penetrate into tissues.

Clearance, on the other hand, quantifies how efficiently a drug is eliminated from the body. It represents the volume of plasma that is completely cleared of the drug over a given period, reflecting the combined effects of metabolism and excretion. Therefore, the relationship between these two pharmacokinetic parameters helps to understand a drug's behavior in the body, including how long it stays active and how quickly it is removed.

The other choices do not capture the full nuance of these concepts: one suggests a direct relationship between absorption and clearance, another incorrectly assigns constancy to one parameter while depicting variability in another without sufficient context, and the last misrepresents the fundamental definitions of both terms.