下列计算不正确的是[ ]
A.（a3）3=a9
B.a6n=（a2n）3
C.（xn+1）2=x2n+2
D.x3·x2=x6
答案：D
选择正确的修辞方法。
老师是辛勤的园丁，我们是祖国的花朵。 [ ]
A、比喻
B、拟人
He doesn’t know how ____________.[ ]
A. to keep health
B. to stay healthy
C. keeping fit
D. keeps healthy
