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Reading comprehension -TOEFL- Lesson 149 (Đọc hiểu -TOEFL- Bài 149)

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There are many theories of aging, but virtually all fall into the category of being hypotheses with a minimum of supporting evidence. One viewpoint is that aging occurs as the body's organ systems become less efficient. Thus failures in the immune system, hormonal system, 5 and nervous system could all produce characteristics that we associate with aging. Following a different vein, many current researchers are looking for evidence at the cellular and sub cellular level. It has been shown that cells such as human fibroblasts (generalized tissue cells) grown in culture divide only a limited number of times 10 and then die. (Only cancer cells seem immortal in this respect.) Fibroblast cells from an embryo divide more times than those taken from an adult. Thus some researchers believe that aging occurs at the cellular level and is part of the cell's genetic makeup. Any event that disturbs the cell's genetic machinery such as mutation, 15 damaging chemicals in the cell's environment, or loss of genetic material, could cause cells to lose their ability to divide and thus bring on aging. Other theories of aging look at different processes.

Chronological aging refers to the passage of time since birth and 20 is usually measured in years. While chronological age can be useful in estimating the average status of a large group of people, it is a poor indicator of an individual person's status because there is a tremendous amount of variation from one individual to the next in regard to the rate at which biological age changes occur. For 25 example, on the average, aging results in people losing much of their ability to perform strenuous activities, yet some elderly individuals are excellent marathon runners.

Another type of aging is cosmetic aging, which consists of changes 30 in outward appearance with advancing age. This includes changes in the body and changes in other aspects of a person's appearance, such as the style of hair and clothing, the type of eyeglasses, and the use of a hearing aid. Like chronological aging, it is frequently used to estimate the degree to which other types of aging have occurred. 35 However, it is an inaccurate indicator for either purpose because of variation among individuals and because a person's appearance is affected by many factors that are not part of aging, including illness, poor nutrition, and exposure to sunlight.

1. The author believes the theories of aging are

2. In line 7, the word "evidence" refers to

3. The word "vein" in line 6 is closest in meaning to

4. The author of the article points out that cancer cells

5. The word "culture" in line 9 is closest in meaning to

6. It can be inferred from the passage that fibroblast cells

7. As explained in this passage, the theory of aging which examines the cellular level would NOT assign which of the following as a cause of aging?

8. According to the passage, chronological aging is not a good indicator of an individual's status regarding aging because

9. The author implies all of the following about cosmetic aging EXCEPT

Grammar Easy Grammar Medium Grammar - Difficult
1->25 26->49 50->75 76->99 100->125 126->164
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