看谁算得又快又准。   

38+10- 40=                          58+30-20=                       51- 40+5=   

64 -20+10=                          66+8-30=                         96-20-10=

Jack does his homework ________ Mary. So they both always get good grades in the exams.

A．so careful as

B．as carefully as

C．so carefully as

D．as careful as