原书 PDF 第 1666 页
wh-疑问词 + to-v 作宾语
（1）There isn't any difference between the two. I really don't know ____.
A. where to choose B. which to choose
C. to choose what D. to choose which(全国高考)
(2) I've worked with children before, so I know what ____ in my new job.
A. expected B. to expect C. to be expecting D. expects(全国高考,00-19)
如何分析上句中的 which to choose 和 what to expect?
见 infinitive ，expect ，when 。
wh-疑问词 + to-v 作介词的宾语
（1）Alice wasn't sure how much to tip the porter.
(2) Have you any idea how to open this packet? 上两句中的 wh-疑问词 + to-v 作什么成分？
wh-疑问词 + to-v 结构常常用作介词的宾语：
I'm not sure about what to do. 我不能肯定应当干什么。
但是,这个介词常常是可以省略的,如:
I have no idea how to open it or what to do with it. (Dan Brown, The Da Vinci Code) 我既不知道怎样打开它，也不知道怎样处置它。（《达·芬奇密码》）