下列运算正确的是( )
A.-3ab+5ab=2a2b2 | B.(-2a2)2•a3=4a7 | C.3a2b•5ab4c=8a 3b5c | D.(-a)6÷a3=a2 |
(-xm-1yn+1)3=( )
A.-x3m-3y3n+3 | B.x3m-3y3n+3 | C.-x3m-1y3n+1 | D.x3m-1y3n+1 |