除去下表内各物质中含有的少量杂质，写出除杂试剂，并填写分离方法．

在五千多年的发展历程中，中华民族形成了以改革创新为核心的团结统一、爱好和平、勤劳勇敢、自强不息的伟大民族精神。（   ）

    It is Saturday. The Browns are at home. Mrs. Brown is in the kitchen. She is making lunch. Mr. Brown isn't in the living room. He is outside. He is washing his car. The car is new and very beautiful. Jim is playing football with some boys. Where is his sister, Sue? She's watching TV in her bedroom with her friend, Ann.

Nian is a ____.

高斯用直尺和圆规作出了正十七边形,如图, 正十七边形的中心角∠AOB的度数近似于(    )