大学英语四级开头句，结尾句，中间段句子 - 7(4)

? 比较对比法

例：

People who believe in the beneficial side may have some arguments as follows. To begin with, farmers can earn more money by working in the cities. Most of them will send part of their income back home to help their families. What’s more, these farmers will help develop the cities in many ways. According to a recent survey, most of the construction projects in big cities are actually done by farmers.

By contrast, some people argue that farmer migration may give rise to a series of negative effects. They worry that much land will be deserted in the country. In addition, it is also believed that rising crimes in cities are partly related to this migration.

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分析：文章利用By contrast对农民工迁移到城市这一现象所带来益处与弊端进行了对比分析。

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? 因果法

例：

The hamburger is the most popular food item in the United States. Every year Americans consume billions of them. They are sold in expensive restaurants and in humble diners. They are cooked at home on the kitchen stove or over a barbecue grill in the backyard. Why are they so popular? First, a hamburger is extremely easy to prepare. It is nothing more than a piece of ground beef, cooked for a few minutes. Then it is placed in a sliced bun. Nothing could be simpler. Even an unskilled cook can turn out hundreds of them in an hour. Besides that, the simple hamburger can be varied in many ways. You can melt some cheese on top of the beef to create a cheeseburger. You can also add some grilled bacon for an interesting flavor contrast. In addition, you can garnish the hamburger with other things such as lettuce, tomato, onion, mushrooms, avocado, pickles, hot pepper, ketchup, relish, mayonnaise, mustard or whatever you wish!

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分析：文章先在第一段的结尾用问句提出汉堡为什么这么受欢迎，紧接着下一段以原因列举展开。

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? 例证法

例：

Take my neighbor as an example. There are three members in their family and the two adults were laid off last year. The only child will have to drop out of school next semester. In order to help them, I donated all my money—300 Yuan to pay the tuition. And I plan to call on others to donate more money. Though I cannot do a lot, I have given love which is like a lamp in a dark place where light is most needed.

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