下列运算正确的是[ ]
A.a+a=2a2
B.(3a2)2=6a4
C.(-3a+2)(3a-2)=9a2-4
D.ab+ba=2ab
答案:D
The start of a new year brings hope — hope _____ better health, more happiness and greater success.
A.among
B.for
C.over
D.on
类风湿性关节炎手部关节破坏严重,常出现哪些畸形()
A.峰谷畸形
B.尺偏畸形
C.鹅颈畸形
D.扣眼畸形
E.望远镜畸形