I really can’t thank you enough， sir —

How I wish I ________ in medicine instead of history when I was at college!

81 Male and female students are quitedifferent from each other ______ the age at which they begin to develop anintellectual self-discipline

When you don’t know some words in reading, it is not a good idea in a dictionary at once.

May I open thewindow to let in some fresh air —_____.