Final answer:
Presynaptic modulation typically takes place at axoaxonic synapses, where one neuron's axon terminal modulates neurotransmitter release from another neuron's axon.
Step-by-step explanation:
Presynaptic modulation occurs at axoaxonic synapses, which is option B. Axoaxonic synapses are unique because they involve a synapse between the axon terminal of one neuron and the axon of another neuron.
This type of synapse can modulate the activity of the postsynaptic neuron by controlling the amount of neurotransmitter released.
Therefore, presynaptic modulation typically affects synaptic transmission at subsequent synapses by either enhancing or inhibiting the release of neurotransmitters from the presynaptic terminal.