Concept: This question tests your understanding of synaptic transmission, specifically where neurotransmitters bind to elicit a response.

Why (D) is correct: When an action potential reaches the axon terminal, neurotransmitters are released into the synaptic cleft. These neurotransmitters then diffuse across the cleft and bind to specific receptor sites located on the post-synaptic membrane. This binding initiates a response in the post-synaptic neuron.

Why other options are wrong:

A) Membranes of synaptic vesicles contain neurotransmitters, but not their receptors.

B) The pre-synaptic membrane releases neurotransmitters, it does not have receptors for them to bind to initiate a signal in the post-synaptic neuron.

C) Tips of axons (axon terminals) are involved in releasing neurotransmitters, not receiving them via receptors.

NEET Tip: Remember the flow: Pre-synaptic neuron releases neurotransmitters $\to$ Synaptic cleft $\to$ Post-synaptic membrane receptors bind neurotransmitters.

Correct Answer: (D)