In an earthworm nerve impulse transmission experiment, students were asked to test the inhibitory effects of some unknown compounds. Upon the addition the students observed that there was no action potential generation at all. On comparing to the known compounds mentioned below, predict the unknown compound?

The answer is lidocaine. It is used in anaesthesia to numb perceptions such as pain, discomfort, itching, and etcetera. It works by blocking the sodium ion channels of the nerves. Therefore it inhibits depolarization of nerves, consequently, blocking impulse generation and transmission across the axon of neurons.