—Do you think you will fail in the math

The Community Representative is a position designed for people with a strong desire to do something

rewarding and _____ some money.[      ]

A. earned

B. to earning

C. earning

D. earn

机油粘度是随温度变化的，温度升高，粘度变小，温度变低，粘度增大。机油粘度随温度变化的特性称为安定性。

血气分析采血抗凝剂用（）

A.枸橼酸钠

B.肝素

C.EDTA盐

D.草酸盐

E.去纤维蛋白法

通过血吸虫和绦虫的学习，谈谈寄生虫对寄主的危害，寄生虫更换寄主的生物学意义。