Why Is It That Caffeine, Which Acts as a Receptor

Why is it that caffeine, which acts as a receptor blocker, functions as a stimulant?

A) The target of caffeine often inhibits the release of excitatory neurotransmitters.
B) Caffeine blocks receptors involved in reuptake, thereby enhancing neurotransmitter action.
C) Caffeine blocks enzymatic degradation, thereby enhancing neurotransmitter action.
D) The stimulant effects of caffeine are the result of expectation and are not dependent on receptor activity.