8×17×125 =17×(8×125)运用了乘法[ ]
A.交换律
B.结合律
C.交换律和结合律
答案:C
一个圆的半径扩大3倍,它的面积就比原来多2倍.______.(判断对错)
Tom insisted _____ history instead of business at university, but his mother insisted that he _____ her advice. [ ]
A. on studying, take
B. to study, must take
C. on studying, took
D. in studying, should take