用括号里所给单词的正确形式填空。
He felt very sad because he answered most of the questions _____________ (correct).
It is difficult for the boy ________ (swim) across the river.
Many people cut down trees ____________ (make) more money.
Hurry up! The film will start at 7;00 , there’s little time ___________(leave) for us now.
Lang Lang has been a famous__________ (piano) at the age of thirteen.