It is said that the new school ________ 20 million yuan will soon be completed.
A：cost
B：costing
C：costs
D：to cost
Nobody knew who was the first ________ at school that morning when the window was broken.
长江沿江地带四大城市群中，城镇最密集的是（ ）
双曲线C的中心在原点，右焦点为F(233,0)，渐近线方程为y=±3x．
（Ⅰ）求双曲线C的方程；
（Ⅱ）设直线l：y=kx+1与双曲线C交于A、B两点，问：当k为何值时，以AB为直径的圆过原点．
