问题
单项选择题
The machines are made () at full speed.
A．work
B．working
C．to work
D．to be worked
答案
参考答案：C
解析：
make...do的被动形式是...be made to do。故选C。
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The machines are made () at full speed.
A．work
B．working
C．to work
D．to be worked
参考答案：C
解析：
make...do的被动形式是...be made to do。故选C。