What kind of channels are located in the input region?
a. voltage gated channels opened by neurotransmitter molecules
b. ligand gated channels opened by neurotransmitter molecules
c. voltage gated channels opened by a change in charge across the membrane
d. ligand gated channels opened by a change in charge across the membrane

The correct answer is option B ( ligand gated channels opened by neurotransmitter molecules).

Explanation:

Input region or postsynaptic region or dendrite is the site of neuron cell which receives the impulse from the pre-synaptic neuron at the synaptic junction.

The cell membrane of the dendrite is embedded with ligand-gated channels which opens up in response to the ligand (neurotransmitters) produced by the neurotransmitter vesicle of axon or output region of neuron.

The neuromuscular junction is such a case where acetylcholine receptors present in the dendrite opens in the presence of acetylcholine.

Thus, option B ( ligand-gated channels opened by neurotransmitter molecules) is the correct option.