下列各式运算正确的是( )
A.a3+a-2=a
B.a3-a-2=a5
C.a3•a-2=a
D.a3÷a-2=a
答案:C
I'm sorry. I can't agree what you said. [ ]
A. to
B. with
C. about
D. on
高压管道加工中,相邻两管道的外壁不得相碰,间距必须大于()mm。
A.10
B.30
C.40
D.50