1. He kept his head _____ water when he began to learn swimming, but he raised his head now and then
______ scientists know where a storm will happen, winds will suddenly change, carrying the storm to a new direction.
When doing your history homework on the Civil War by typing in details to Google, a list of related books will ______ .
He _______ to go to Tsinghua University to study after graduating from high school, so he is working very hard.
The thief went into the house at midnight, only ______ by the policemen hiding there.
. It is because English is being widely used at present _______.