The possibility of a way out of the difficulty never _____ to the captain and his crew.

A．happened

B．occurred

C．appeared

D．flashed

下列关于胃的主细胞的描述，哪一项是错误的（）。

A.多位于胃底腺的底部

B.胞质嗜碱性

C.顶部胞质内有许多酶原颗粒

D.基部胞质内有密集排列的滑面质网和高尔基复合体

E.能分泌胃蛋白酶原