People should open the window in the morning to make air ______ in order to keep the indoor air fresh.
World leaders have to face the fact that ________ global warming has become perhaps ________ most complicated issue.
I'm a fresh hand so I don't think I can do it well. -________Something attempted,something done.
The couple overjoyed ________ words on hearing their son survive the airplane crash by a miracle.
Around the world there are many young people________a great deal of money on listening to pop or rock music.
A British scientist has predicted that parents who lose children in accidents may be able to clone “copies” to________ them within 50 years.