More people like Living in a city now, especially young people who like new and modern things. Most people think it is much ____ （容易） to find work in a city . They think there are a lot of ____ (有乐趣的) things to do and places to see in the city . There are also many ____ (选择) of public transport. When they feel tired, they can eat in good restaurants, visit museums, go to cinemas and go to parks.

    ____ （然而）, in my opinion, living in the city will ____ (花费) more . What's more, the ____ (人口) of the city is getting bigger and bigger.  so it's a ____（遗憾） that the city is always ____ （拥挤的） noisy and dirty. And It is very difficult to find a good place where people can enjoy ____（和平） and fresh air. So We should ____ （改善） the serious situation.

已知生产一件芯片，若是合格品可盈利400元，若是次品则亏损50元．

（Ⅰ）试估计生产一件芯片为合格品的概率；并求生产3件芯片所获得的利润不少于700元的概率．

（Ⅱ）记ξ为生产4件芯片所得的总利润，求随机变量ξ的分布列和数学期望．

1848年，马克思、恩格斯联合发表《____》，标志着马克思主义诞生，1859年，达尔文发表《____》，完整地确立了生物进化论说。