题目

Can you tell me ______ the railway station? A . how I can get to B . how can I get to C . where I can get to D . where can I get to 答案：A18．已知点A是抛物线y2=4x的对称轴与准线的交点，点B是其焦点，点P在该抛物线上，且满足|PA|=m|PB|，当m取得最大值时，点P恰在以A，B为焦点的双曲线上，则双曲线的实轴长为（　　）A．$\sqrt{2}$-1B．2$\sqrt{2}$-2C．$\sqrt{2}$+1D．2$\sqrt{2}$+2