管线加油车排空回收油箱的方法之一,是将回收油箱中的燃油,经()后,注入飞机油箱。
A.添加防菌剂
B.化验
C.过滤
D.化学测水
参考答案:C
“十一五”时期,我国工业固体废物综合利用率提高到( )。
A.60%
B.50%
C.56%
D.65%
It's quite warm here; we ________ turn the heating on yet . [ ]
A. couldn't
B. mustn't
C. needn't
D. wouldn't