The poor child stood there, and ________ what to do, turned to his father for help.
Today, we’ll discuss a number of cases_______ beginners of English fail to use the language properly.
_______ on earth do you suppose_______ this?
American women were______ the right to vote until 1920 after many years of hard struggle.
We should keep ourselves_______ of the latest development of science and technology.
To those_______ in martial arts(武术), the period from 1972 to 1975 is often said_______ the Bruce Lee era.