问题

I’m so busy while he is _____ play[ ]
A: on
B: at
C: on the
D: at the
B: at
C: on the
D: at the
正确答案是:
同类题型
How can they learn anything ______ they spend all their spare time watching television?
Thomas was _______ excited at the exciting news that he could hardly say a word.
era school ______teachers have to work as a team, instead of fighting againsteach other