After living in Shanghai for 20 years, the couple returned to the small village ______ they grew up.
Scientists say it may be five or ten years _______ it is possible to test this medicine on human patients.
I send you 100 dollars today, the rest _______ in a year.
Taking a plane is the quickest _______ to get to Tibet.
Though he is a(n) _______ worker, he works very hard.
_______ two exams to worry about, I have to work really hard this weekend.