Các bạn giải thích giúp mình nhé Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the questions from 30 to 34 Scientists do not yet thoroughly understand just how the body of an individual becomes sensitive to a substance that is harmless or even wholesome for the average person. Milk, wheat, and egg, for example, rank among the most healthful and widely used foods. Yet these foods can cause persons sensitive to them to suffer greatly. At first, the body of the individual is not harmed by coming into contact with the substance. After a varying interval of time, usually longer than a few weeks, the body becomes sensitive to it, and an allergy has begun to develop. Sometimes it's hard to figure out if you have a food allergy, since it can show up so many different ways. Your symptoms could be caused by many other problems. You may have rashes, hives, joint pains mimicking arthritis, headaches, irritability, or depression. The most common food allergies are to milk, eggs, seafood, wheat, nuts, seeds, chocolate, oranges, and tomatoes. Many of these allergies will not develop if these foods are not fed to an infant until her or his intestines mature at around seven months. Breast milk also tends to be protective. Migraines can be set off by foods containing tyramine, phenathylamine, monosodium, glutamate, or sodium nitrate. Common foods which contain these are chocolate, aged cheeses, sour cream, red wine, pickled herring, chicken livers, avocados, ripe bananas, cured meats, many oriental and prepared foods (read the labels!). Some people have been successful in treating their migraines with supplements of B-vitamins, particularly B6 and niacin. Children who are hyperactive may benefit from eliminating food additives, especially colorings, and foods high in salicylates from their diets. A few of these are almonds, green peppers, peaches, tea, grapes. This is the diet made popular by Benjamin Feingold, who has written he book. “Why your Child is Hyperactive”. Other researchers have had mixed results when testing whether the diet is effective. 30. Question 30. What does the passage mainly discuss? A. reactions to foods B. food and nutrition C. infants and allergies D. a good diet 31. Question 31. According to the passage, the difficulty in diagnosing allergies to foods is due to _____. A. the vast number of different foods we eat B. lack of a proper treatment plan C. the similarity of symptoms of the allergy to other problems D. the use of prepared formula to feed babies 32. Question 32. The phrase "set off" is closest in meaning to ______. A. relieved B. identified C. avoided D. triggered 33. Question 33. What can be inferred about babies from this passage? A. They can eat almost anything. B. They should have a carefully restricted diet as infants. C. They gain little benefit from being breast fed. D. They may become hyperactive if fed solid food too early. 34. Question 34. The author states that the reason that infants need to avoid certain foods related to allergies has to do with the infant's ______. A. lack of teeth B. poor metabolism C. underdeveloped intestinal tract D. inability to swallow solid foods