压缩工业风和仪表风为什么要净化？
参考答案：
经过压缩的风里含有一定量的水和油，如果不除去会造成管浅冻结，堵塞仪表。
So far nobody has claimed the money_______in the library. [ ]
A. discovered
B. to be discovered
C. discovering
D. having discovered
— Why don’t you go into the office ,John
—I have ______ my office keys at home.
A．forgot
B．kept
C．leaving
D．left
