题目

已知双曲线的一个焦点，点P位于该双曲线上，线 的中点坐标为（0,2），则双曲线的标准方程为______． 答案： Henry always forgets things he has done. Yesterday he forgot__________ and looked for it everywhere.          A. to post the letter                B. to have the letter posted    C. to have posted the letter      D. having posted the letter