如果2是一元二次方程x2=x+c的一个根，那么常数c是 [ ]
A．2
B．-2
C．4
D．-4
答案：A
Not until he took off his sunglasses _______ him.
A．I recognized
B．I did recognize
C．did I recognize
D．do I recognize
汉译英：“投保人”，正确的翻译为（）。
A．policyholder
B．premium
C．insured
D．insurant
