______ chemistry is a branch of chemistry．
A．Applying B．Apply C．Applied D．To apply
More and more high-rise buildings have been built in big cities ______ space．
A．in search of B．in place of
C．for lack of D．for fear of
---We haven’t seen each other for ages．
---No, I don’t remember how many years ago _______ I last saw you．
A．it was that B．was it that
C．it was when D．was it when
We are still at the airport．If it weren’t for the delayed flight, we _______ the concert right now．
A．can be enjoying B．must have enjoyed
C．would be enjoying D．should have enjoyed
_____ his research paper, Professor Reagan experienced various hardships and loneliness for nearly half a year．
A．Accomplishing B．To accomplish
C．Accomplished D．Having accomplished
____ the flight to New York will be delayed is _____ I’m especially worried about．
A．When; what B．Whether; that
C．When; that D．Whether; what
