Tom rushed into the house his mother was cooking.A. as B. before C. while D. after

问题补充：

Tom rushed into the house his mother was cooking.

A. as

B. before

C. while

D. after

答案：

A. as

B. before

(答案→)C. while

D. after

解析：句意：他的妈妈正在做饭的时候，汤姆跑进了房子。while当…时候，强调动作同时发生，必须和延续性的动作连用，多用现在进行时态；as多强调伴随的关系，强调渐进性；before在…之前；after在…之后，故选C.