材质为铝合金的管道、管件及阀门，宜用（）做脱脂剂。
A.煤油
B.工业酒精
C.二氯乙烷
D.四氯乙烷
参考答案：B
We have two spare rooms downstairs, ______ has been used for more than two months.
A．neither of them
B．none of which
C．none of them
D．neither of which
正循环压井与反循环压井各有什么特点？
