—Tom, why don't you do your homework in your room?    

—I _____it already.    [ ]

A. did                    

B. have done    

C. do                    

D. will do

轮胎纵向花纹与横向花纹相比（）。

A.耐磨性能好

B.滚动阻力小

C.噪音更大

D.不易夹石子