- When should I hand in my paper?— Your paper must _as soon as the bell_.A. hand in; rings

问题补充：

- When should I hand in my paper?

— Your paper must _as soon as the bell_.

A. hand in; rings

B. hand in; will ring

C. be handed in; will ring

D. be handed in: rings

答案：

A. hand in; rings

B. hand in; will ring

C. be handed in; will ring

(答案→)D. be handed in: rings

解析：被动语态与as soon as的用法。paper作主语 (为“交卷”的承受者)，故要用被动语态，as soon as表示“一……就……”，从句用一般现在时代替一般将来时。故选择D。