The solution that will cause contraction in the muscle fiber is acetylcholine and norepinephrine.
What are these solutions?
Acetylcholine is a neurotransmitter that is released at the neuromuscular junction, which is the synapse between a motor neuron and a muscle fiber. When acetylcholine binds to receptors on the muscle fiber, it triggers a series of events that lead to the contraction of the muscle fiber.
Norepinephrine is a neurotransmitter that can also cause muscle contraction. However, it does so by a different mechanism than acetylcholine. Norepinephrine binds to receptors on the sarcolemma that are different from the acetylcholine receptors. When norepinephrine binds to these receptors, it activates an enzyme called adenylate cyclase.
Complete question:
Which solution(s) will cause contraction in the muscle fiber?