题目

Transportation and communication networks bring people together. Yet sometimes people themselves create barriers to transportation and communication. In some countries, laws stop people from moving freely from place to place. Over the centuries, many groups of people have been denied the freedom to travel because of their race, religion, or nationality. In the Middle Ages, for example, Jews were often forbidden to move about freely within certain cities. South Africa's government used to require black Africans to carry passes when they travel within the country. Some governments require all ci关于下列说法正确的是（　　） A、其M电子层上的电子为8个B、该元素位于第三周期第ⅥA族C、最高正化合价为+2价D、该元素是长周期元素