It has been announced that candidates(应考者) remain in their seats until all the papers hav

问题补充：

It has been announced that candidates(应考者) remain in their seats until all the papers have been collected.

A. can

B. will

C. may

D. shall

答案：

A. can

B. will

C. may

(答案→)D. shall

解析：在规章中告诫应考者，在收完所有试卷前“必须”留在教室里。