单选49.________theyheardtheshoutfo
49. ________ they heard the shout for help，they rush out. A. Immediately B. The moment C. The while D. All the above 为什么选择D 呢？我没见过C 这种说法,AB 都见过。
就是说，前面三个答案都可以，C.The while/moment=as soon as ,while是名词，类似词语：after a while/moment