Certain drug acts at synapses and affects the action of neurotransmitter substances. The table shows the effects of four different drugs.
Drug Effect
I. Inhibits the enzyme cholinesterase.
II. Prevents the release of acetylcholine.
III. Competes with acetylcholine at receptor sites.
IV. Inhibits the enzyme which destroys nor-adrenaline.
Which two drugs would prevent a skeletal muscle from responding to an electrical stimulus in the presynaptic neuron?
(a) I and II
(b) I and IV
(c) II and III
(d) II and IV