Hearing the news about the crash of Air France Flight 447, he became very concerned _______ his daughter on board.

The teacher said ______ wanted to go to the cinema must be there before 6:00.

Nancy spent half an hour _______ playing the piano every day.

Have you realized the difficulty we have ____ the problem?

_____ April 14, many people in Yu Shu lost their lives _____ the earthquake. [ ]