—_______ have you lived in Binzhou?
—For about ten years.
A:How soon
B:How often
C:How long
D:How much
下列选项中,能使关于x的一元二次方程ax2﹣4x+c=0一定有实数根的是( )
“今大道既隐,天下为家。”这种状况始于( )