题目内容：

Though giant pandas may appear perfectly happy chewing bamboos, scientists recently discovered that they would rather have something sweeter. Scientists chose        because the animals are herbivores (食草动物), which would mean that they would love sweets. However, the plant they choose, the bamboos, has a very           sugar content and is therefore not considered sweet. Could this mean that pandas have          their hobby for sweet things?

The pandas were given six kinds of sweet liquids that are        found in fruits and vegetables. They were also given        at the same time. In each of the taste tests, the animals        the natural sweeter liquids and ignored the water           . They ate up all the sweet liquids and the water was left untouched.

What was even more interesting is that when the scientists        the water with five different man-made sweeteners, ones that humans find delicious, the pandas were not as          . In these tests, they picked the water instead. The scientists believe that it could be either because pandas found them to be too          or not sweet enough and that the mixture could not          the pandas.

The scientists were not too           by the results, since pandas in zoos have always shown a preference for treats like apples, sweet potatoes and even mooncakes. Scientists believe that the pandas may have once           sweeter foods that were available in the lowland areas that they used to live in. But when human settlement in the lowland areas        them to the bamboo forests in the mountains, they had no          but to settle for the almost sugarless plants.

1.A. horses B. bears C. monkeys D. pandas

2.A. high B. simple C. low D. different

3.A. lost B. followed C. started D. kept

4.A. specially B. hardly C. naturally D. rarely

5.A. fruits B. water C. bamboos D. oxygen

6.A. picked B. hid C. rejected D. shared

7.A. largely B. gradually C. occasionally D. completely

8.A. mixed B. covered C. exchanged D. replaced

9.A. funny B. picky C. perfect D. interested

10.A. salty B. sweet C. sour D. hot

11.A. harm B. save C. attract D. change

12.A. Delighted  B. surprised C. disappointed D. concerned

13.A. Enjoyed   B.disliked C. controlled D. ignored

14.A. Encouraged B. forced C. introduced D. guided

15.A. desire B. chance C. wonder D. choice