[解析]
(1)C.细节理解题.根据文章第一段,Cities usually have a good reason for being where they are,like a nearby port or river.People settle in these places because they are easy to get to and naturally suited to communications and trade.New York City,for example,is near a large harbour at the mouth of the Hudson River.城市的形成通常有一个很好的理由,比如附近的港口或河流.人们在这些地方定居是因为它们很容易到达,而且自然适合通讯和贸易.例如,纽约市就在哈德逊河河口的一个大港口附近.可知,人们选择在河边或港口设城是因为交通方便,便于做生意.而纽约就是在哈德森河口附近的一个大港口,故纽约吸引早期移民的原因是它的地理位置,结合选项,故选C.
(2)B.细节理解题.根据文章第二段,Of the first 20,000 people who dug for gold,4,000 got rich.About 100 of these stayed rich men for the rest of their lives.在最初2万个掘金的人中,有4000人发财了,其中大约100人的余生都是富人.可知,在最初挖黄金的两万人中有4000人变富有,所以是五分之一的人变富了,结合选项,故选B.
(3)B.细节理解题.根据文章最后一段,The city was crowded with disappointed people with no interest in settling down,and when they heard there were new gold discoveries in Alaska,they left Dawson City as quickly as they had come.城里挤满了失望的人们,他们对安顿毫无兴趣,当他们听说阿拉斯加有新的金矿发现时,他们很快就离开了道森城.可知,人们离开Dawson的主要原因是听说在Alaska发现了黄金,也就是他们要去别的地方寻找发财的机会.结合选项,故选B.
(4)A.主旨大意题.根据文章内容,第一段简要介绍城市发展的原因,引出Dawson这一城市的兴起,第二段介绍了该城市兴起的原因,第三段介绍人们选择离开该城市的原因及现在的状况,所以全文围绕Dawson这个城市的发展起伏而展开的.结合选项,故选A.