— Shall I help clean the kitchen, Mom?  

— Thank you. But you ________ it because I can do it myself. [      ]

A. mustn't have done

B. wouldn't have done  

C. mightn't have done

D. don't have to do

根据2004年中国移动CMCC GPRS巡检规定：DT掉线率指标满分标准是（）。

A.0.005

B.1%

C.1.5%

D.2%