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29.What can be inferred about the footprints found in French caves mentioned in the last paragraph? (A)They show more detail than the Laetoli prints. (B)They are of more recent origin than the Laetoli prints. (C)They are not as informative1 as the Laetoli prints. (D)They are more difficult to study than the Laetoli prints
30.Which of the following terms is defined in the passage? (A) "hominids" (line 3) (B) "arch" (line 9) (C) "photogrammetry" (line 16) (D) "silicon2 resin3 molds"(line 29)
Questions 31-40
The livelihood4 of each species in the vast and intricate assemblage of living things depends on the existences of other organisms. This interdependence is sometimes subtle, sometimes obvious. Perhaps the most straight forward dependence5 of one species on another occurs with parasites7, organisms that live on or in other living things and derive8 nutrients9 directly from them. The parasitic10 way of life is widespread. A multitude of microorganisms( including viruses and bacteria) and an army of invertebrates11 – or creatures lacking a spinal12 column (including crustaceans13, insects, and many different types of worms ) –make their livings directly at the expense of other creatures. In the face of this onslaught, living things have evolved a variety of defense14 mechanisms16 for protecting their bodies from invasion by other organisms.
Certain fungi17 and even some kinds of bacteria secrete18 substances known as antibiotics19 into their external environment. These substances are capable of killing20 or inhibiting21 the growth of various kinds of bacteria that also occupy the area, thereby22 eliminating or reducing the competition for nutrients. The same principle is used in defense against invaders23 in other groups of organisms. For example, when attacked by disease-causing fungi or bacteria, many kinds of plants produce chemicals that help to ward6 off the invaders.
Members of the animal kingdom have developed a variety of defense mechanisms for dealing24 with parasites. Although these mechanisms vary considerably25, all major
groups of animals are capable of detecting and reacting to the presence of "foreign" cells. In fact, throughout the animal kingdom, from sponges to certain types of worms, shellfish, and all vertebrates (creatures possessing a spinal column), there is evidence that transplants of cells or fragments of tissues into an animal are accepted only if they come from genetically26 compatible or closely related individuals.
The ability to distinguish between "self" and "nonself", while present in all animals, is most efficient among vertebrates, which have developed an immune system as their defense mechanism15. The immune system recognizes and takes action against foreign invaders and transplanted tissues that are treated as foreign cells.
31. What does the passage mainly discuss? (A) how parasites reproduce (B) how organisms react to invaders (C) how antibiotics work to cure disease (D) how the immune systems of vertebrates developed
32. The word "intricate" iii line 1 is closest in meaning to (A) difficult (B) widespread (C) critical (D) complex 33. The expression "an army" in line 6 is closest in meaning to (A) an illness (B) an attack (C) a large number (D) a distinct type
34. The expression "an army in line 6 is closest in meaning to (A) an illness (B) an attack (C) a large number (D) a distinct type
35. According to the passage, some organisms produce antibiotics in order to (A) prevent disease in humans (C) fight off other organisms (D) create new types of nutrients
35.The word "vary" in line 19 is closest in meaning to (A) differ (B) endure (C) balance (D) contribute
36. The word "they" in line 23 refers to (A) sponges, worms and shellfish (B) vertebrates (C) individuals (D) transplants
37. According to the passage, a transplant of tissue between genetically incompatible organisms will result in the transplanted tissue (A) becoming a parasite (B) being treated as an invader (C) altering its genetic makeup (D) developing a new immune system 点击收听单词发音
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