题目

下列有关物质分类的说法中正确的是A.由同种元素组成的物质一定是纯净物 B.由同种元素组成的物质叫单质C. 氧化物一定是化合物D. 只含一种元素的物质一定不是混合物 答案：CBobby was a dog that went every moming to a baker's shop to fetch twelve bread roll for its owner. However. when Bobby returned back one day, it had only eleven rolls. Bobby's owner wants to know what had happened, but he followed Bobby to the baker's shop the next day Instead taking the road home as usually. Bobby took another road and went up to a farm. There was a poorer little dog with a broken leg. Bobby was offered the roll to the little dog. The owner was very proud of Bobby and rewarded itself a nice big bone. Later, the owner's family never grew tired of tell everybody how kind and clever Bobby was