Stimulation of a muscle fiber by a motor neuron occurs at the neuromuscular junction, the transverse tubules, the myofibril, or the sarcoplasmic reticulum?

The neuromuscular junction connects the nervous system to the muscular system via synapses between efferent nerve fibers and muscle fibers. So, the stimulation of a muscle fiber, by a motor neuron occurs at the sarcolemma of the neuromuscular junction due to the release of a neurotransmitter (Acetylcholine).Thus, the correct answer is option (A), 'The neuromuscular junction'.