C. It is becoming thinner.  D. It is ruined by chemicals.

　　25. Farmers can do the following things to prevent soil erosion EXCEPT ______.

　　A. rotating their crops  B. using effective fertilizers

　　C. using new plowing methods  D. building terraces on hilly fields

　　II. Vocabulary. (10 points, 1 point for each)

　　Directions: Scan the following passage and find the words which have roughly the same meanings as those given below. The number in the brackets after each word definition refers to the number of paragraph in which the target word is. Write the word you choose on the Answer Sheet.

　　Most of us buy vitamins for one of three reasons. Either we believe that they are prophylactic, that is they will ward off advancing ill, or they are therapeutic and will deal with the ills we have already, or finally we may believe they are wonder drugs and will lift us into a state of super health. We are protected from some of these wild imaginings by the laws which control advertising but even without false promises we still believe that vitamins will "do us good".

　　Belief is a very potent state of mind and the power of the placebo pill is never underestimated in clinical trials used to test new drugs. A placebo is a harmless substance given to one group of patients in the trial and it is similar in taste and appearance to a new drug which is given to a second group of patients. Theoretically the drug should cure or relieve any symptoms and the placebo should have no effect. Often these trials produce surprising results and the placebo group recovers as well as the group taking the new drug.

　　Vitamins B and C cannot be retained in the body, so if we take more than we need of these, they are soon excreted in the urine. Taking too much of the fat soluble vitamins can be dangerous and vitamins A and D should never be taken indiscriminately. Vitamin E has not been found to have any toxic effect in large doses, but neither do there seem to be any noticeable benefits. This is an unexplored area in vitamin research and the only known advantages of vitamin E are confined to specialized medical cases.

　　26. to prevent something from harming you (Para. 1)

　　27. very good and effective (Para. 1)

　　28. situations or ideas that are not real or true (Para. 1)

　　29. having a powerful effect on your body or mind (Para.2)

　　30. a series of testing to find out whether something works (Para.2)

　　31. to make a pain or problem less severe (Para.2)

　　32. gets well after an illness, accident, shock (Para.2)

　　33. not thinking carefully before making a choice (Para.3)

　　34. poisoning (Para.3)

　　35. examples of particular situations, problems (Para.3)

　　III. Summarization. (20 points, 2 points for each)

　　Directions: In this section of the test, there are ten paragraphs. Each of the paragraphs is followed by an incomplete phrase or sentence which summarizes the main idea of the paragraph. Spell out the missing letters of the word on your Answer Sheet.