At present, what _____ most heavily on American people is the terrorist accident (恐怖事件).
— You have to believe in yourself. No one else will, if you don't. — __________. Confidence is really important.
I am concerned __________ it that I can't concentrate __________ my work because of headache.
His daughter couldn't concentrate __________ her studies with all that noise going on.
Mr. Bill Clinton was elected __________ President of the United States in __________ 1990s.
At __________ present we are going through a hard time, but I'm sure __________ things will get better in the near future.