加氢装置氢气中（）含量高，容易造成反应器床层超温。
A、惰性气体
B、甲烷
C、硫化氢
D、一氧化碳和二氧化碳
参考答案：D
—Why didn't you go to see the film yesterday?
—Because I _____ it twice. [ ]
A. had seen
B. have seen
C. saw
D. has seen
以下哪一种食物维生素A含量最丰富（）
A.菠菜
B.洋芋
C.广柑
D.动物肝
E.牛奶
