问题描述：
会英语的帮帮忙,几道语法题,
1THE radio of the work done by the machine______the work done on it is called the efficiency of the machine.
A against B with C to D for
2 Once more I have to leave Beijing,____I have been living for 8 years .
A that B where Cwhich D as
3 I was almost alsleep when I suddenly heard someone_____at the door.
A be knoking B knocking C to knock D having knocked
1THE radio of the work done by the machine______the work done on it is called the efficiency of the machine.
A against B with C to D for
2 Once more I have to leave Beijing,____I have been living for 8 years .
A that B where Cwhich D as
3 I was almost alsleep when I suddenly heard someone_____at the door.
A be knoking B knocking C to knock D having knocked
问题解答：
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