现实中有一些两难情境，考验着我们选择的智慧。

陈某因被拖欠450万巨款讨债无门，铤而走险在海珠桥上演“跳桥秀”；某制衣厂几名工人因与厂方发生劳务纠纷，也相约到海珠桥“跳桥秀”。他们的行为，堵塞了交通，扰乱了社会秩序。对此，有专家建议将“恶意跳桥”列入刑法，加大惩罚力度。

用权利与义务的有关知识分析“跳桥秀”。

下图A，B处分别为（    ）

阅读理解

    There are four seasons in China. March, April and May make the spring. June, July and August make the summer season. September, October and November make the autumn season. The rest（剩下）of months make the winter season.

    The Australia seasons are the opposite（相反的）of ours. When it's spring in China, it is autumn in Australia.

    Australia is in the south（南方）of the earth. June, July and August are the winter months. The summer is in December, January and February. It's very hot there, too.

    Near the North Pole（北极）there are two seasons. The winter nights are long. For more than two months you can't see the sun, even at noon. The summer days are long. For more than two months, the sun never sets（落下）, and there's no night.

如图所示，一束光从半球面上的A点沿半径方向射入半球形玻璃砖，已知半球形玻璃砖的球心为O，且光线到达半球形玻璃砖下表面处时可以发生折射和反射．请画出这束光线从射入玻璃砖到射出玻璃砖的完整光路图．

计算：（$\frac{2}{3}$﹣$\frac{1}{2}$）×（﹣6）=____ ．