计算(a3b)2÷(ab)2的结果是 （ ）
A．a3
B．a4
C．a3b
D．a4b
B.
题目分析：原式=a6b2÷a2b2
=a4．
故选B.
—Is Mary ?
—No, she is a girl.
A．twelve years old; fourteen years old.
B．twelve years old; fourteen -year -old.
C．twelve - year - old; fourteen years old.
D．twelve - year - old; fourteen - year -old.
一个商标被认定为驰名商标之后，作为驰名商标的保护期限有多长
