泵是炼油化工装置不可缺少的（）机械
A.气体输送
B.液体输送
C.固体输送
参考答案：B
My brother was making a-lot of noise _____ I was doing my homework. [ ]
A. but
B. and
C. while
国家提倡健康公民自愿献血的年龄是
A．16周岁至40周岁
B． 18周岁至28周岁
C．18周岁至55周岁
D．18周岁至45周岁
