Which of the following statements best summarizes excitation-contraction coupling?

a. a series of events in which an action potential triggers the release of chemical messengers.
b. a series of events in which calcium gradients are used to convey a signal to the muscle fiber to enact contraction.
c. a series of events in which an electrical stimulus is conveyed to a muscle fiber to enact contraction.
d. a series of events in which actin binds myosin to enact contraction.

C. A series of events in which an electrical stimulues is conveyed to a muscle fiber to enact contraction.

Explanation:

The excitation-contraction coupling is the physiological process that converts an electrical stimulus to a mechanical response; it is the action potential generated in the sarcolemma and the start of a muscle contraction. Electrical signals called action potentials travel through the neuron's axon, which branches through the muscle and connects individuals fibers at a neuromuscular junction.

the answer to your question is a plant

b. the carbon cycle ensures living things have a source of hydrogen