若2a2bm-1与-7an+1b4是同类项,则m+n=______.
依题意得:n+1=2m-1=4,
解得m=5,n=1.
当m=5,n=1时,m+n=5+1=6.
I'm sorry I'm busy now. If I have time, I ________ to the zoo with you. [ ]
A. would go
B. will go
C. am going
D. went
关于改建后从事水路运输的老旧船舶,下列说法正确的是()
A、一类船舶可以改建为二类船舶
B、四类船舶可以改建为三类船舶
C、一、二、三类船舶之间不得相互改建
D、四、五类船舶之间不得相互改建