Question

the complex formed by an axon and its muscle fiber is called the
neuromuscular junctions.
motor units.
nervous units.
motor end plates.
synaptic terminals.

Explanation:

A motor unit is composed of a single motor neuron (axon) and all the muscle fibers it innervates. Neuromuscular junctions are the synapses between the axon terminal and the muscle fiber. Motor end plates are part of the muscle fiber membrane at the neuromuscular junction. Nervous units is not a standard term in this context. Synaptic terminals are just the ends of axons.

Answer:

motor units.