Chloroplasts are most commonly found in the green (mesophyll) cells of photosynthesizing plants. Any part of a plant that is green is capable of photosynthesis and therefore contains cells containing chloroplasts.
Answer:
wrong subject and none of theses is the answer :(
the answer is differentiation
Excitation-contraction coupling refers to the series of events that begins with the excitation of the sarcolemma in response to stimulation by a neurotransmitter, and results in the release of calcium ions from the sarcoplasmic reticulum.
Hence, option D is the 1st process that starts the excitation-contraction coupling.