Once you decide to choose a topic to write an effective paragraph, the first key to writing is to write a good topic sentence. The topic sentence does two things: it tells the reader what the topic of the paragraph is, and it says something about that topic. What the topic sentence says about the topic is called the controlling idea; it is the point of the paragraph, and every other sentence in the paragraph must be related to this point.
The topic sentence should be the first sentence in the paragraph unless there is some special reason for placing it some where else. When the topic sentence is the first sentence of the paragraph, the reader immediately knows what you intend to discuss. In addition, you have the topic sentence to refer to as you make each of the other sentences in the paragraph, so that you can be sure that each of those sentences refers to your subject and to your controlling idea. Sometimes experienced writers put the topic sentence at the end
A. because the reader immediately knows what you are intended to discuss
B. because you have the topic sentence to refer to as you write on
C. because you are not experienced
D. both A and B
The food we eat seems to have profound effects on our health. Although science has made enormous strides in making food more fit to eat, it has, at the same time, made many foods unfit to eat. Some research has shown that perhaps eighty percent of cancer is related to diet as well, especially cancer of the colon (结肠). Different cultures are more prone (倾向于) to contract certain illnesses because of the food that is characteristic in these cultures. That food is related to illness is not a new discovery. In 1945, government researchers realized that nitrates and nitrites, commonly used to preserve colour in meats, and other food additives, caused cancer. Yet, these carcinogenic additives remain in our food, and it becomes more difficult all the time to know which things on the packaging labels of processed food are helpful or harmful.
The additives which we eat are not all so direct. Farmers often give penicillin to cows and chickens, and because of this, penicillin has bee
A. scientist have made all the food fit to eat
B. only in recent years have people found that food is related to certain illnesses
C. all kinds of cancer are related to diet
D. some additives are harmful to our health
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