为什么球墨铸铁的机械性能比普通灰铸铁好，而铸造性能却比普通灰铸铁差？

She ____________ a big mouth. [ ]

A. has

B. is

C. are

—Your father doesn't look well these days.

—Yes. He has had a toothache, but he keeps ______ going to the dentist. [ ]

A. putting off

B. getting off

C. setting off

D. taking off

直线职能制

红楼梦：林黛玉

A．孙悟空：西游记

B．罗贯中：三国演义

C．水浒传：宋江

D．聊斋志异：蒲松龄

〈煤矿矿井机电设备完好标准〉中要求机车照明有效光距不小于（），警铃、音响距离大于40m