写作思路：

  1. 快餐在中国十分流行，它是现代快节奏社会的最佳反映; 2. a. 快餐受欢迎有两条原因： b. 然而，从营养角度来讲，快餐却差强人意;3. 对快餐还是以偶尔品尝为宜。

  范例：

  Fast Food

  Fast food is becoming more popular in China, especially among children and teenagers. Today, it“s certainly difficult to think of any other single thing that represents the fast pace of modern society as powerfully as fast food.

  There are several reasons for its popularity. First, it is very convenient and saves a lot of time. The trends of modern society seem to all point to one ultimate goal —— saving time, and fast food well serves this purpose. You just go into a fast food restaurant, order your food, and your food is ready in no time. You can either eat it there or take it away. Second, its popularity is also attributed to the clean and comfortable environment of fast food restaurants, the excellent service, and the guaranteed qualith of food.

  However, in terms of nutrition, fast food is far from satisfactory. It usually does not compose a balanced diet and is low in nutritional value. Thus, doctors suggest that people, especially children, eat fast food as little as possible.   Although cooking at home is time — consuming and the following washing-up tiresome, it offers healthy and delicious meals your body likes and needs. Fast food is only a good choice when you are in a hurry and turn to it once in a while.