Here are two more topic sentences:

⑦Going to college is expensive.

⑧Northwestern is a university in Illinois.

Of the two topic sentences, ⑦is too general and ⑧is a factual one, so they allow no development. From above we know an effective topic sentence has three characteristics: it includes a subj(转载自论文之家http://www.papershome.com，请保留此标记。)ect and a controlling idea; it is limited; and it lends itself to development.

Topic sentence usually appears at the beginning, but may also be found in the middle or at the end, of a paragraph.

We can also see how every philosopher reflects the social life at his day. Plato and Aristotle, in the slave-owning society of ancient Greece, Thought man’s highest state was contemplation rather than activity. In the Middle Ages St. Thomas believed in a regular feudal system of nine ranks of angels. Herbert Spencer, in the time of free competition between capitalist, found the key to progress in the survival of the fittest. Thus Marxism is seen to fit into its place as the philosophy for the workers, the only class with a future.

----J.B.S. Haldane

The topic sentence of this paragraph is the first sentence “Every philosopher reflects the social life of his day.”

When a writer places a topic sentence at the end of a paragraph, it often serves as a climax to the details that come before it. Biology major Ben Wright, in a paragraph from a report focusing on the benefits of genetic engineering, places the topic sentence last.

Recently scientists used a bacterium called agro bacterium tumefactions to transfer a special insect and disease resistant gene into the cells of walnut tree plants. Texts proved that the insect and disease resistant characteristics at the special gene had been successfully in corporeity into the walnut plant’s genetic material. Clearly, this genetic feat has major implications for growers who produce American 300-million-a-year walnut crop, but moreover, it also has important implications for health-minded consumers’ when researchers are able to transfer insect and disease resistant genes o all food-bearing plants, then genetic engineering can be used to protect us from the poisonous insecticides and pesticides that growers use on their crops.

Sometimes, when a writer leaves out a topic sentence the discussion must be so clear that the controlling idea of the paragraph is strongly implied.

The room is located on the fifth floor of a high building. One third of its total floor space is taken up by a double bed. Facing it, in the corner behind the door, stands a cupboard loaded with pats, bowls, dishes, bottles and bags of rice and flour. A desk completely fills the gap between the bed and the wall with the window. Behind the desk is a chair, the only one in the room

威廉希尔app   论文写作指导