[填空题]Manmade fibers have only been used to make{{U}} (36) {{/U}}for a little over a century, but their use is quite{{U}} (37) {{/U}}nowadays. Rayon, the first manmade fiber commercially produced in the United States, appeared in 1910. In 1939, nylon, the first chemically{{U}} (38) {{/U}}fiber, was first produced in this country on a commerical basis. Ever since, the number of manmade fibers has{{U}} (39) {{/U}}into including more than 20 types. Although the{{U}} (40) {{/U}}of manmade clothing fibers is long, rayon remains one of the most popular of all time, and that is why we continue to produce it in such great{{U}} (41) {{/U}}. Rayon is made of cellulose, a naturally occurring{{U}} (42) {{/U}}found in cotton and in certain vegetables, like celery, of all things. The cellulose in rayon has been recycled and treated to make it a useful fiber for clothing. {{U}} (43) {{/U}}. Most rayon washes well, too, although it does shrink when it is washed in hot water. {{

[填空题]Manmade fibers have only been used to make{{U}} (36) {{/U}}for a little over a century, but their use is quite{{U}} (37) {{/U}}nowadays. Rayon, the first manmade fiber commercially produced in the United States, appeared in 1910. In 1939, nylon, the first chemically{{U}} (38) {{/U}}fiber, was first produced in this country on a commerical basis. Ever since, the number of manmade fibers has{{U}} (39) {{/U}}into including more than 20 types. Although the{{U}} (40) {{/U}}of manmade clothing fibers is long, rayon remains one of the most popular of all time, and that is why we continue to produce it in such great{{U}} (41) {{/U}}. Rayon is made of cellulose, a naturally occurring{{U}} (42) {{/U}}found in cotton and in certain vegetables, like celery, of all things. The cellulose in rayon has been recycled and treated to make it a useful fiber for clothing. {{U}} (43) {{/U}}. Most rayon washes well, too, although it does shrink when it is washed in hot water. {{

[单项选择]Two main techniques have been used for training elephants, which we may call respectively the tough and the gentle. The former method simply consists of setting an elephant to work and beating him until he does what is expected. Apart from any moral considerations this is a stupid method of training, for it produces a resentful animal who at a later stage may well turn man-killer. The gentle method requires more patience in the early stages, but produces a cheerful, good-tempered elephant who will give many years of loyal service.
The first essential in elephant training is to assign to the animal a single mahout who will be entirely responsible for the job. Elephants like to have one master just as dogs do, and are capable of a considerable degree of personal affection. There are even stories of half-trained elephant calves who have refused to feed and pained to death when by some unavoidable circumstance they have been deprived of their own trainer. Such extreme cases must proba
A. can have unpleasant consequences later
B. is the most effective method available
C. increases the time it takes to train the animal
D. ensures loyal service for years to come

[单项选择]16-20