It was never clear ________ the man hadn't reported the accident sooner.(2011·江苏)
The living room is clean and tidy, ________ a dining table already laid for a meal to be cooked.
Scientists say it will be five or six years ________ it is possible to test this medicine on humans.
You are students in the No.168 Senior High School now, but you _______ in different junior high schools for three years.
Being injured in the leg made _______ impossible for him to walk his way home.
It is believed that a new kind of drug _____ by the scientists and they are hopeful that they will succeed in a few months.