舱室作业环境的氧气含量应不低于（），二氧化碳含量应不高于（），始能作业。
A．8%/2%
B．8%/5%
C．18%/2%
D．18%/5%
参考答案：C
The children _____ the windows already, so the classroom looks much brighter.[ ]
A. are cleaned
B. will clean
C. are cleaning
D. have cleaned
具行气之功的药物是（）
A.草果
B.厚朴
C.砂仁
D.白豆蔻
E.草豆蔻
