Li Dong is a schoolboy. He's twelve. He lives in Beijing. He gets up at 6:30. He reads English and Chinese in the morning. He has breakfast at 7:00. In the afternoon, he has three classes. He often does the homework after dinner. Li Dong likes playing football. His mother's hobby is planting flowers. His father is interested in collecting stamps. He often shows the nice stamps to Li Dong and his mum. They like the stamps very much.

苏伊士运河沟通了（   ） 

在历史学习中，我们应学会区分历史史实和历史结论。下列各项中，属于历史结论的是（  ）

在城市，排在第一位的癌症是____；在农村，排在第一位的癌症是____；在青少年和儿童中，排在第一位的恶性肿瘤是____。