The diagram below shows a simplified representation of a chemical synapse during synaptic transmission.
Which row, from A to D, correctly identifies the parts labelled P to S in the diagram?
P: ligand-gated Na+\text{Na}^+Na+ channel, Q: synaptic vesicle, R: synaptic cleft, S: voltage-gated Ca2+\text{Ca}^{2+}Ca2+ channel
P: voltage-gated Ca2+\text{Ca}^{2+}Ca2+ channel, Q: synaptic vesicle, R: synaptic cleft, S: neurotransmitter receptor
P: voltage-gated Ca2+\text{Ca}^{2+}Ca2+ channel, Q: mitochondrion, R: postsynaptic membrane, S: neurotransmitter receptor
P: sodium-potassium pump, Q: synaptic vesicle, R: synaptic cleft, S: ligand-gated channel