若A、B为5阶方阵，且Ax=0只有零解，且r(B)=3，则r(AB)=_________________.
IfI_________Bush,I_________neverstartanywar.
A、am,will
B、was,will
C、were,would
D、had,would
Howlongdidtheconcert______?
A、go
B、last
C、take
D、make
—It’sawarmday,isn—’Yes,tit?it’s__________cold.Ijustwearajacket.
A、notabit
B、abit
C、alittle
D、notalittle
_____girlinwhiteis_____friendofmine.Andwearealsoclassmates.
A、The,the
B、A,the
C、A,/
D、The,a