Scientists say it may be five or six years ___ it is possible to test this medicine on human patients.
The speech by the mayor of Shanghai before the final voting for EXPO 2010 is strongly impressed _______ my memory.
After he retired from office, Rogers ______ painting for a while, but soon lost interest.
Mr. Smith was very disappointed to see the car he had had _____ went wrong again.
Tom rushed out in a hurry, ______ the door ______.
This computer doesn’t work properly, because the operating system has .