（Ⅰ）求 $a$ 的值；

（Ⅱ）以坐标原点 $O$ 为极点， $x$ 轴正半轴为极轴建立极坐标系，射线 $l_1:\theta =\text{α}(\rho \ge 0,0<\alpha <\frac{\pi }{2})$ 与曲线 $C$ 交于不同的两点 $O,A,$ 与直线交于点 $B$ ，若 $\left|OA\right|=\left|AB\right|$ ，求 $\alpha$ 的值。

下列计算正确的（  ）   　　

    The first teacher-parent meeting would be held in the school. To the little boy's disappointment(失望), his mother said she would go. He felt sorry for her face. She was very beautiful, but there was a big scar (疤痕) on her right face. The boy never talked about it with his mother.
At the meeting, the people noticed the mother’s kindness and beauty though she had the scar. But the little boy hid himself. After the meeting, the teacher asked his mother carefully. "How did you get the scat on your face?" The mother answered. "When my son was a baby, he was once in a room that caught fire. Everyone was too afraid to go in because the fire was out of control. At that time, I rushed in As I was running towards his bed. I saw a piece of wood coming towards his bed. I threw myself over him to protect him. I was knocked down. Luckily, a fireman came in and saved both of us. But I got the scar." She touched her face." This scar will be here for ever, but I have never felt sorry for what I did."
    At that moment, the little boy came out with his eyes wet. He held his mother’s hand for the rest of the day.

《中国资本主义与国内市场》一书记载：1933年，工业总产值中（包括制造业和矿冶业），消费资料工业产值占70%以上，而生产资料工业产值不到30%。1936年，生产资料工业产值占工业总产值的23%，而消费资料工业产值则占工业总产值的77%。这一材料反映的实质是