下列计算正确的是（　　）

已知f（x）=|x+a|，g（x）=|x+3|﹣x，记关于x的不等式f（x）＜g（x）的解集为M．

2016年11月11日和11月18日，北京市和平街第一中学的约四百名学生开展了以“规划未来，成就梦想”为主题的生涯规划社会实践活动。在本次活动中为青少年群体提供实践平台的企业包括：国美电器、京师律师事务所、富德生命人寿、全聚德集团、人民邮电出版社、盈科律师事务所、凯撒旅游、中国平安、宜信财富、新东方、团中央未来网、上海夸客优富企业管理顾问有限公司、北京市第一中级人民法院、三元食品、码高机器人教育科技有限公司，共十五家企业单位。

已知a是有理数，则下列结论正确的是（　　）

There is a new park near Andy's home. It's fine today. Andy and his family are in the park now. On their left, there is a café. On the right, there is a big lake. There are many flowers and trees around the lake. There's a small hill behind the lake. Near the lake, there are two signs（标记）. One says, "Don't swim in the lake."But you can go boating on the lake. There is a beautiful garden in the middle of the park. There are green grass and beautiful flowers in it. There are some small shops between the lake and garden. The park is so nice. Andy and his family like it very much.