下面计算一定正确的是[ ]
A．a3a3=2a6
B．a0=1
C．（2ab2）2=4a2b4
D．（a2+b2）2=a4+b4
答案：C
— What are you doing, Mary?
— I'm looking _____ my mobile phone. I want to call my father. [ ]
A. after
B. like
C. for
点火过早会使发动机（）
A.功率下降
B.功率提高
C.省油
D.产生爆震
