Question

The old lady did not know ___________when the house caught fire.

A．how to do	B． what to do
C． how to do it	D．what to do it.

Answer 1

B

试题分析：句意：当房子着火的时候，那位女士不知道做什么。因为do是及物动词，所以需要宾语，how不能作宾语；故排除A；如果用疑问词what，它可以作do的宾语，就没有必要用it，故排除D；故选。