Americans eat _______ vegetables each person today as they did 20 years ago..
The pressure _____ causes Americans to be energetic, but it also puts them under a constant emotional strain (过度紧张).
_____ it or not, his discovery has created a stir in scientific circles.
After the Arab states won independence, great emphasis was laid on expanding education, with girls as well as boys _____ to go to school.
There's a man at the reception desk who seems very angry and I think he means _____ trouble.
That was so serious a matter that I had no choice but _____ the police.