Question

【题目】The old lady didn't knowwhen the house caught fire.
A.how to do
B.how to do it
C.what to do
D.what to do it

Answer 1

【答案】C
【解析】句意：当房子着火时，那位老太太不知道怎么办。how是副词，不能充当动词后的宾语。宾语what to do中what可以充当do的宾语，不能用how充当。故排除AD两项。it代指前面出现的事物，本句中it没有要指代的事物，故排除B项。故选C。