11. Acids are chemical compounds that，in water solution，have a sharp taste，a corrosive action on metals，and the ability to turn certain blue vegetable dyes red.

酸是一种化合物，它在溶于水时具有强烈的气味和对金属的腐蚀性，并且能够使某些蓝色植物染料变红。

12. Billie Holiday‘s reputation as a great jazz-blues singer rests on her ability to give emotional depth to her songs. Billie Holiday’s

作为一个爵士布鲁斯乐杰出歌手的名声建立在能够赋予歌曲感情深度的能力。

13. Essentially，a theory is an abstract，symbolic representation of what is conceived to be reality.

理论在本质上是对认识了的现实的一种抽象和符号化的表达。

14. Long before children are able to speak or understand a language，they communicate through facial expressions and by making noises.

儿童在能说或能听懂语言之前，很久就会通过面部表情和靠发出噪声来与人交流了。

15. Thanks to modern irrigation，crops now grow abundantly in areas where once nothing but cacti and sagebrush could live.

受当代灌溉（技术设施）之赐，农作物在原来只有仙人掌和荞属科植物才能生存的地方旺盛的生长。

16. The development of mechanical timepieces spurred the search for more accurate sundials with which to regulate them.

机械计时器的发展促使人们寻求更精确的日晷，以便校准机械计时器。

17. Anthropology is a science in that anthropologists use a rigorous set of methods and techniques to document observations that can be checked by others.

人类学是一门科学，因为人类学家采用一整套强有力的方法和技术来记录观测结果，而这样记录下来的观测结果是供他人核查的。

18. Fungi are important in the process of decay，which returns ingredients to the soil，enhances soil fertility，and decomposes animal debris.

真菌在腐化过程中十分重要，而腐化过程将化学物质回馈于土壤，提高其肥力，并分解动物粪便。

19. When it is struck，a tuning fork produces an almost pure tone，retaining its pitch over a long period of time.

音叉被敲击时，产生几乎纯质的音调，其音量经久不衰。

20. Although pecans are most plentiful in the southeastern part of the United States，they are found as far north as Ohio and Illinois.

虽然美洲山河桃树最集中于美国的东南部但是在北至俄亥俄州及伊利诺州也能看见它们。