问题
选择题
They learned it all by themselves. That is to say nobody told them ________ .
A．what to do it
B．how to do it
C．where to do
D．when to do
答案
答案：B
题目分析：句意：他们是自学的这些技能。也就是说没有人告诉他们该如何去做这些事。本句考查特殊疑问词+to do做宾语；A项中it多余；C和D项少了it；结合句意可知，B项符合要求；故选B。