Final answer:
The functional connection between a neuron and a skeletal muscle fiber is called a synapse, specifically a neuromuscular junction, where acetylcholine is released to initiate muscle contraction.
Step-by-step explanation:
The functional connection between a neuron and a skeletal muscle fiber is known as a synapse. Specifically, this connection is called a neuromuscular junction, which is a type of synapse. At the neuromuscular junction, the axon terminals of a motor neuron make a specialized synaptic structure with the muscle fiber sarcolemma.
During this process, the synaptic end bulbs of the motor neurons release a neurotransmitter called acetylcholine, which binds to receptors on the sarcolemma. This triggers the opening of ligand-gated ion channels, leading to a depolarization of the sarcolemma and initiating muscle contraction. Therefore, the correct answer to the student's question is A. synapse.