∠1与∠2互补且相等，∠3与∠2是对顶角，则∠3的一半为 [ ]
A.70°
B.80°
C.45°
D.30°
答案：C
—You can get such information on computer.
—But I don't know how _______ the Internet. [ ]
A. search
B. searching
C. searched
D. to search
后金是谁建立的（）
A、蒙哥铁木耳
B、皇太极
C、努尔哈赤
D、铁木真
