烃类液压油分为几个类型?
参考答案:
烃类液压油分为两个类型,一是矿物油型液压油,二是合成烃型液压油。
(2013·临沂市一模)Usually there might be a lot of accidents in the heavy fog.I happened to witness ________ this morning.
A.it
B.those
C.each
D.one
要求:(1)意见合理,具体可行;(2)条理清楚,语言简明;(3)字数不超过300字。