試題詳解

66.After a muscle cell contracts, which of the following must occur for the muscle to stop contracting?
(A) Calcium ions must be pumped back into the endoplasmic reticulum；
(B) Calcium ions must flow out of the endoplasmic reticulum；
(C) Calcium ions must flow into the muscle cell；
(D) Calcium ions must be pumped out of the muscle cell.