THE HEINEMANN TOEFL COURSE PRACTICE TEST 2 READING PART 5 (Questions 42-50)

THE HEINEMANN TOEFL COURSE

PRACTICE TEST 2

READING

PART 5 (Questions 42-50)

The cause of tooth decay is acid, which is produced by bacteria in the mouth. The acid removes minerals from tooth enamel, allowing tooth decay to begin; the saliva in your mouth encourages remineralization and neutralizes the acid. The rate at which bacteria in the mouth produce acid depends on the amount of plaque on the teeth, the composition of the microbial flora, and whether the bacteria of the plaque have been "primed" by frequent exposure to sugar. To keep your teeth healthy, a regular dental hygiene program should be followed. Removing plaque with a toothbrush and dental floss temporarily reduces the numbers of bacteria in the mouth and thus reduces tooth decay. It also makes the surfaces of the teeth more accessible, enabling saliva to neutralize acid and remineralize lesions. If fluoride is present in drinking water when teeth are forming, some fluoride is incorporated into the enamel of the teeth, making them more resistant to attack by acid. Fluoride toothpaste seems to act in another way, by promoting the remineralization of early carious lesions. In addition to a regular dental hygiene program, a good way to keep your teeth healthy is to reduce your intake of sweet food. The least cavity-causing way to eat sweets is to have them with meals and not between. The number of times you eat sweets rather than the total amount determines how much harmful acid the bacteria in your saliva produce. But the amount of sweets influences the quality of your saliva. Avoid, if you can, sticky sweets that stay in your mouth a long time. Also try to brush and floss your teeth after eating sugary foods. Even rinsing your mouth with water is effective. Whenever possible, eat foods with fiber, such as raw carrot sticks, apples, celery sticks, etc., that scrape off plaque, acting as a toothbrush. Cavities can be greatly reduced if these rules are followed when eating sweets. 42 What does this passage mainly discuss? A Good nutrition Food with fiber Ways to keep your teeth healthy Fluoridization and cavities B C D 43 According to the passage, all of the  following statements about plaque are true EXCEPT A It consists of acid producing bacteria It is not affected by eating sweets It can be removed from teeth by brushing and flossing It reduces the positive effect of saliva B C D 44 We can infer from the passage that one benefit of fluoride to healthy teeth is A It strengthens tooth enamel It stimulates saliva production It makes teeth whiter It is a replacement for brushing and flossing in dental care B C D 45 The word "it" in line 9 refers to A dental floss bacteria removal of plaque plaque B C D 46 What can be concluded from the passage about sweets? A All sweets should be avoided. Sweets should be eaten with care. It is better to eat sweets a little at a time throughout the day. Sticky sweets are less harmful than other sweets. B C D 47 The word "scrape off" in line 22 is closest in meaning to A repel rub together with remove dissolve B C D 48 It can be inferred from the passage that foods with fiber are A sugary expensive sticky abrasive B C D 49 According to the passage, the value of eating foods with fiber is that A they contain Vitamin A they are less expensive than a toothbrush they are able to remove the plaque from your teeth they contain no sugar B C D 50 The author of the passage states that the amount of acid produced by the bacteria in your saliva increases A with the amount of sweets you eat with the number of times you eat sweets if you eat sweets with your meals if you eat sticky sweets B C D

ANSWER KEY

42. C The correct answer is (C) because this is the central idea of the passage. Answers (A), (B), and (D) are supplementary ideas. 43. B   The correct answer (B) is found in lines 3-6, which state that the rate at which bacteria in the mouth produce acid depends in part on whether the bacteria of the plaque have been "primed" by frequent exposure to sugar. This means that frequent exposure to sugar causes plaque to produce more bacteria. Answers (A) and (C) are true according to lines 7-9 and answer (D) is true according to lines 9-10. 44. A   The correct answer (A) is found in lines 11—13 some fluoride is incorporated into the enamel of the teeth, making them more resistant to attack by acid. It can be inferred that being resistant to attack is similar to strengthen. Answers (B), (C), and (D) are not mentioned in the passage as benefits of fluoride to teeth. 45. C   The correct answer is (C) because this is the noun phrase that logically makes the surfaces of the teeth accessible to healthy saliva. 46. B   The correct answer is (B) because the passage discusses the relation of sweets to cavities and suggests how to reduce the risk of cavities if sweets are eaten. Lines 23-24 state ... if these rules are followed when eating sweets. Following rules implies being careful when eating sweets. (A) is too strong based on the information in the passage; (C) is incorrect according to lines 16-17; (D) is incorrect according to line 19. 47. C   Clues to the meaning of "scrape-off are the immediate context eat foods... that scrape-off plaque and the phrase acting as a toothbrush. 48. D   From the context of lines 21-23 we have the image of food rubbing against the teeth as a toothbrush does. Such an action is abrasive. 49. C   The correct answer (C) is found in lines 22-23. ... that scrape off plaque, acting as a toothbrush is similar in meaning to... remove the plaque from your teeth. (A), (B), and (D) are not mentioned in the passage. 50. B   The correct answer (B) is found in lines 17-19 which states The number of times you eat sweets rather than the total amount determines how much harmful acid the bacteria in your saliva produce. (A) is incorrect because the amount of sweets influences the quality of your saliva, not the amount of acid. (C) and (D) are incorrect because they are not mentioned in the passage as related to acid production.