①铁钉表面产生气泡；②液体由无色逐渐变为浅绿色；③铁钉的质量减轻；④液体的质量减轻．

1999年11月29日，全球首次“数字地球国际会议”在北京召开。世界近30个国家和地区的4 000多位科学家参加了这次会议，研讨21世纪“数字地球”的发展战略。中国政府和学术界在“数字地球”的基础上提出了“数字中国”的构想。构想中的“数字中国”将建立一个统一完整的国家公用信息网。它集成了国家信息网、国土资源信息网、长江流域监控网等网络的信息，并将促进这些系统的综合利用。据此回答：

下列不属于“数字中国”服务领域的工作是（  ）

已知α∈R，$\sin \kappa +3\cos \alpha =\sqrt{5}$，tan2α=（　　）

B

    Are you sorry for not traveling during the National Day? If you stay a t home at that time, I think you are very lucky. Why? Because there are too many people everywhere. In many places of interest in China, it's too crowded to do anything.

    It was very crowded in the West Lake on October 1st, 2013. You even couldn't take photos for you or your friends. All what we could see were people. It was reported that there were about 13 people per meter by the lake. My friends told me they could see nothing but many tourists(游客) on the Broken Bridge(断桥). "We couldn't walk if the people in front of us didn't walk," he said. He showed us a photo near the West Lake. In the photo, we hardly found him out, there were too many people.

    So some people give the advice that we should not have the gold week(黄金周) any more. But other people say no about this advice. What's your idea of it? Are you sorry now for not traveling during the gold week? I love staying at home more than traveling next National Day.