Why are you looking for Mary in a hurry, John —The boss is wondering where she _______ and how long she _______ there.

Everyone was when they heard this news.

enables the pilot of an airliner totake off, fly and land in _____.

It’s hard for the young people to imagine what _____ conditions their parents once lived under.

The smoggy weather has made us realizeterrible problems we are laced with．