在数轴上到原点距离等于2的点所标示的数是[ ] A．－2 B．2 C．±2 D．

It ____ for three hours and the ground is too wet toplay on, so the sports meet  _____.    [ ]

A. was raining;has been put off      

B. has been raining;has been put off        

C. has rained; put off      

D. has been raining;has put off

下列表现中不是左侧大肠癌常见症状的是（）

A.粪便形状变细

B.血便或脓血便

C.进行性贫血

D.腹绞痛

E.直肠指检扪到肿块

下列关于有机化合物的说法正确的是

A．乙酸和乙酸乙酯可用Na₂CO₃溶液加以区别

B．戊烷（C₅H₁₂）有两种同分异构体

C．乙烯、聚氯乙烯和苯分子均含有碳碳双键

D．糖类、油脂和蛋白质均可发生水解反应

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