下列运算正确的是[ ]

A．a+2a²=3a²

B．a⁸÷a²=a⁴

C．a³a²=a⁶

D．（a³）²=a⁶ 

—Anna, can you come to play volleyball?   

—                 I have to finish my work first.      [ ]

A. OK   

B. Thanks  

C. Sorry, I'm afraid I can't  

D. Not all right