English Skills 10th Edition by John Langan, Zoe Albright

Exercise 47

Each group of sentences below could be written as a short paragraph. Circle the letter II of the topic sentence in each case. To find the topic sentence, ask yourself, "Which is a general statement supported by the specific details in the other three statements" Begin by trying the example item below. First circle the letter of the sentence you think expresses the main idea. Then read the explanation.
Example
A) If you stop carrying matches or a lighter, you can cut down on impulse smoking.
B) If you sit in no-smoking areas, you will smoke less. O You can behave in ways that will help you smoke less.
C) You can behave in ways that will help you smoke less.
D) By keeping a record of when and where you smoke, you can identify the most tempting situations and then avoid them.
Explanation Sentence a explains one way to smoke less. Sentences b and d also provide specific ways to smoke less. In sentence c, however, no one specific way is explained. The words ways that will help you smoke less refer only generally to such methods. Therefore, sentence c is the topic sentence; it expresses the author's main idea. The other sentences support that idea by providing examples.
A) This car costs less than comparable models.
B) My car is economical.
C) It gets forty-one miles per gallon.
D) After 75,000 miles, I have replaced only the tires and brakes.