37. The main problem of the round-the-clock working system lies in ________.

　　A) the inconveniences brought about to the workers by the introduction of automation

　　B) the disturbance of the daily life cycle of workers who have to change shifts too frequently

　　C) the fact that people working at night are often less effective

　　D) the fact that it is difficult to find a number of good night workers（B）

　　38. The best solution for implementing the 24-hour working system seems to be ________.

　　A) to change shifts at longer intervals

　　B) to have longer shifts

　　C) to arrange for some people to work on night shifts only

　　D) to create better living conditions for night workers（C）

　　39. It is possible to find out if a person has adapted to the changes of routine by measuring his body temperature because ________.

　　A) body temperature changes when the cycle of sleep and wakefulness alternates

　　B) body temperature changes when he changes to night shift or back

　　C) the temperature reverses when the routine is changed

　　D) people have higher temperatures when they are working efficiently（D）

　　40. Which of the following statements is NOT TRUE?

　　A) Body temperature may serve as an indication of a worker’s performance.

　　B) The selection of a number of permanent night shift workers has proved to be the best solution to problems of the round-the-clock working system.

　　C) Taking body temperature at regular intervals can show how a person adapts to the changes of routine.

　　D) Disturbed sleep occurs less frequently among those on permanent night or day shifts.

　　Passage Three

　　Merchant and passenger ships are generally required to have a life preserver for every person aboard and, in many cases, a certain percentage of smaller sizes for children. According to United States Coast Guard requirements, life preservers must be simple in design, reversible, capable of being quickly adjusted to fit the uninitiated individual, and must be so designed as to support the wearer in the water in an upright or slightly backward position.

　　Sufficient buoyancy (浮力) to support the wearer should be retained by the life preserver after 48 hour in the water, and it should be reliable even after long period of storage. Thus it should be made of materials resistant to sunlight, gasoline, and oils, and it should be not easily set on fire.

　　The position in which the life preserver will support a person who jumps or falls into the water is most important, as is its tendency to turn the wearer in the water from a face-down position to an upright or slightly backward position, with his face clear of the water, even when the wearer is exhausted or unconscious.

　　The method of adjustment to the body should be simple, and self-evident to uninitiated persons even in the dark under the confused conditions which follow a disaster. Thus, the life preserver should be reversible, so that it is nearly impossible to set it on wrong. Catches, straps, and ties should be kept to a minimum. In addition, the life preserver must be adjustable to the wide variety of shapes and sizes of wearers, since this greatly affects the position of floating and the self-righting qualities. A suitable life preserver should also be comfortable to wear at all times, in and out of the water, not so heavy as to encourage to take it off on shipboard while the ship is in danger, nor so burdensome that it hinders a person in the water while trying to swim.

　　41. The passage is mainly about ________.

　　A) the uses of life preservers

　　B) the design of life preservers

　　C) the materials for life preservers

　　D) the buoyancy of life preservers（D）

　　42. According to the passage, a life preserver should be first of all, ________.

　　A) adjustable

　　B) comfortable

　　C) self-evident

　　D) self-righting（A）

　　43. United States Coast Guard does NOT require the life preserver to the made ________.

　　A) with as few strings as possible

　　B) capable of being worn on both sides

　　C) according to each wearer’s size

　　D) comfortable and light to wear（A）

　　24. By “the uninitiated individual” (Para. 1, line 6) the author refers to the person ________.

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