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Reading comprehension -TOEFL- Lesson 157 (Đọc hiểu -TOEFL- Bài 157)

Đọc đoạn văn sau và trả lời các câu hỏi:

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 5 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.

10 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 15 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 20 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 25 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. 30 Cavities can be greatly reduced if these rules are followed when eating sweets.

1. What does this passage mainly discuss?

2. According to the passage, all of the following statements about plaque are true EXCEPT

3. We can infer from the passage that one benefit of fluoride to healthy teeth is

4. The word "it" in line 12 refers to

5. What can be concluded from the passage about sweets?

6. The word "scrape off" in line 29 is closest in meaning to

7. It can be inferred from the passage that foods with fiber are

8. According to the passage, the value of eating foods with fiber is that

9. The author of the passage states that the amount of acid produced by the bacteria in your saliva increases

Grammar Easy Grammar Medium Grammar - Difficult
1->25 26->49 50->75 76->99 100->125 126->164
Ôn Tập Ngữ Pháp Phần 1 Ôn Tập Ngữ Pháp Phần 2