The traffic department has taken effective measures ________ the car speed in the town and

________ the traffic accidents.[      ]

A. limiting; cut off  

B. to limit; cut up

C. limiting; cut out  

D. to limit; cut down

具有酸碱两性的是（）

A.氨基酸

B.蛋白质

C.多糖

D.鞣质

E.有机酸