Which statement most accurately describes Action potential refractory period?

A. A period that limits immediate re-excitation of an excitable membrane after depolarisation. B. A hormone that raises plasma calcium through bone, kidney and vitamin-D related effects. C. A phospholipid-rich substance that lowers alveolar surface tension and helps prevent collapse. D. A gastrointestinal hormone that stimulates gastric acid secretion and mucosal growth.