Answer :
The primary reservoir for calcium that is released during excitation-contraction coupling in a skeletal muscle fiber is sarcoplasmic reticulum.
What is the function of sarcoplasmic reticulum?
The sarcoplasmic reticulum is responsible for storeing calcium ions which it releases when a muscle cell is stimulated.
So we can conclude that the primary reservoir for calcium that is released during excitation-contraction coupling in a skeletal muscle fiber is sarcoplasmic reticulum.
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