Tom broke the window but he tried to find ways to escape .
Only after a baby seal is pushed into the sea by its mother _____ to swim.
As is well known, carelessness and irresponsibility _______ many deadly accidents.
They ___________ for two hours
Taiyuan,a city in North China,was struck by a heavy snowfall last week,________serious traffic problems.
It was not until the beginning of the twentieth century________to explore space.