— Is Jack on duty today? — It be him. It's his turn tomorrow.A. mustn'tB. won'tC. can'tD

问题补充：

— Is Jack on duty today?

— It be him. Its his turn tomorrow.

A. mustn

B. won

C. can

D. needn

答案：

A. mustn

B. won

(答案→)C. can

D. needn

解析：考查情态动词表示推测：句意：--今天杰克值日吗？--不可能是他。明天该轮到他。Can’t be用于否定推测“不可能是”，must表示推测的时候，表示“肯定是”，won’t不愿意，needn’t不必，选C。