在迎接神七返回的庆祝活动中，瑞金三中的同学们朝气蓬勃地扭着秧歌，排成了两个正方形阵，每一边有20人，在每个方阵的中心空出了36人的正方形空地，你能算出这个队伍的人数吗？

根据短文内容， 判断正误。
   Robots seems very new to most people. But they have a long history. The first one was made by a Greek inventor, you may see robots are used in factories. They are used to do many dangerous, difficult or boring jobs.
   Some people can't look after themselves and robots are used to help them. For example, some people can't see, many of these people use a dog to help them. In the future, robot dogs might take the place of these guide dogs.
   Robots are also used in American hospital. At one hospital, a robot takes meals from the kitchen to sick people's rooms. It never loses its way because it has a map of the hospital in its computer system.
   In the future, robots will work in space. But robots will never take the place of human being. They can, however, help us in a lot of different ways.

如图，直径为10的⊙A经过点C（0，5）和点O（0，0），点B是y轴右侧⊙A上一点，则cos∠OBC的值为（   ）

区域的开放程度越高，区域内部的自然条件差异越大。