At night, plants _________carbon dioxide and at the same time _________oxygen. So, we may put some in our bedrooms to purify the air.
A. take in, give out B. take up, give off
C. take in, give in D. take off, give up
Only when I left home to go to college ___ how much my mother had done for me.
A. did I realize B. I realized C. had I realized D. I had realized
For many cities in the world, there is no room to spread out farther, _____New York is an example.
A. for which B. in which C. of which D. from which
Beautifully ________ in a quiet spot near the river, the hotel attracts a lot of people to stay.
A. locating B．lies C．situated D．sat
_________ we have been classmates for three years, she hasn’t left me much impression, so I can’t remember her after graduation.
A. SinceB. Although C. Because D. Unless
When and where to build the new factory _____not decided yet .
A. is B. are C. has D. have
