到南极洲考察的最好季节是北半球的（　　）

阅读下列材料：

材料一：

秦统一货币示意图

材料二：元鼎四年（公元前113年），汉武帝取消郡国铸钱的权利，专令水衡都尉所属的钟官、辨铜、均输三官，负责铸造新的五铢钱，名为三官钱。……这次禁令很严格，新币质量又高，盗铸无利可图，所以币制得到较长期的稳定。货币的统一，没有强大的国家力量是不可能的；而货币统一以后，封建国家的经济力量得到加强，专制主义中央集权制度也获得一种经济上的保证。——翦伯赞《中国史纲要》

材料三：公元前221年，秦灭六国，建立了中国历史上第一个统一的多民族的封建中央集权国家，创立了较为完整的政治、经济、文化制度。秦亡汉兴后，继承和发展了秦朝的各种制度，并统治中国300多年。秦汉统一的政治格局为中国文化的大一统提供了现实的社会基础，使中国文化的基本类型得到确定。——摘自王新婷等著《中国传统文化概论》

请回答：

    It was a very foggy day in London. The fog was so 1 that it was impossible to see more than a foot. Buses, cars and taxis were not able to run and were 2 by the side of the road. People were trying to find their way on foot but were losing their way in the3.

    Mr. Smith had a very important meeting at the Houses of Commons and had to get there but no one could 4 him. He tried to walk there but found he was quite 5 Suddenly he met a stranger. The stranger 6 if he could help him.

    Mr. Smith told him where he would go. The stranger told him he would take him there. Mr. Smith thanked him and started to walk there. They talked about the annoying foggy weather on their way.

    The fog was getting thicker every minute but the stranger had no difficulty in 7the way. He went along one street, turn down another, crossed a square and then after about 8 walk, they arrived. Mr. Smith couldn't understand9 the stranger found his way. “It's wonderful,” he said. “How do you find the way in the fog?”

    “It's no 10 at all to me.” said the stranger, “I am blind.”