The diagram depicts a synapse. What are the labelled structures?
- AP: synaptic gap; Q: neurotransmitter; R: vesicle; S: receptor
- BP: synaptic gap; Q: receptor; R: vesicle; S: neurotransmitter
- CP: vesicle; Q: neurotransmitter; R: synaptic gap; S: receptor
- DP: vesicle; Q: receptor; R: synaptic gap; S: neurotransmitter