Scarcely had they settled themselves in their seats in the theatre the curtain went up.A.

问题补充：

Scarcely had they settled themselves in their seats in the theatre the curtain went up.

A. then

B. before

C. when

D. then

答案：

A. then

B. before

(答案→)C. when

D. then

解析：句意为：--他们在剧院一坐下，幕布就升起了。

A .then，在那时

B. before，在---之前

C .when，固定搭配：Scarcely had+完成时 when+一般过去时：一---就=no sooner ---than

D. then在那时