2． 民工对城市的建设所做的贡献
3． 民工的大量流入可能带来的问题

(1The early-1990s finds an unprecedented tide of rural workers flooding into big cities such as Shanghai, Guangzhou, and Beijing. (2)According to a recent survey, in Shanghai alone there are more than 2.5 million migrant workers.
(3)There is an ambivalent feeling towards rural workers. (4)No one denies the important contribution rural workers have made to the urban development. (5)They have done most of dirty, dangerous and underpaid jobs in heavy industries, construction sites and other fields that city residents are unwilling to enter. (6)They have become an indispensable part of urban life to a point where the machinery of a city connot operate without those cogs, though small and unnoticed. (7)Yet an anti-migrant attitude runs consistently through the mainstream of urban consciousness. (8)City residents complain that migrant workers have worsened traffic and sanitation problems and have threatened to take already scarce urban jobs. (9)They also blame them for the sharp rise in the urban crime rate.
(10)Despite the problems posed by migrants, one thing is certain: a grand, prosperous edifice of the city is based on the work of millions of migrant workers.

Exercises:
TV: A Blessing or a Curse
1． 电视已成为人们生活中不可缺少的东西
2． 电视给人们带来的是福是祸
3． 我的看法
My View on the Construction of the Three Gorges Dam
1． 三峡工程的优点
2． 三峡工程的缺点
3． 我的看法
Prospect of the New Age of Science and Technology
1． 新世纪的科技发展迅速
2． 新科技对社会产生的影响
1． 我的看法