如图所示，竖直半圆环中有多条起始于A点的光滑轨道，其中AB通过环心O并保持竖直．一质点分别自A点沿各条轨道下滑，初速度均为零．那么，质点沿各轨道下滑的时间相比较（   ）

    Hi, I 'm Peter. This is the photo of my family. My grandfather is with glasses. He has little hair. The one standing next to him is my father. He is wearing a cap. My grandmother has gray hair. She is a kind woman. She is holding my younger sister. She has short curly hair. The woman standing behind me is my mom. She has straight( 笔直的 ) brown hair. There is a little boy sitting on the table. His name is Paul. He is my brother. He is wearing a green T-shirt and a pair of green socks. It's his favorite color. Which one is my uncle? Well, he is wearing glasses, too. He is in brown shorts and brown shoes. His name is Sam. Now, do you know where he is?

图是中国四大地理区域略图，读图回答下题。

已知双曲线$\frac{x^2}{a^2}-\frac{y^2}{b^2}=1$ $\left(a>0,b>0\right)$的左、右焦点分别为$F_1,F_2$，以$\left|F_1,F_2\right|$为直径的圆与双曲线渐近线的一个交点为$\left(3,4\right)$，则此双曲线的方程为（    ）