12. Billie Holiday‘s reputation as a great jazz-blues singer rests on herability to give emotional depth to her songs.
13. Essentially， a theory is an abstract， symbolic representation of whatis conceived to be reality.
14. Long before children are able to speak or understand a language， theycommunicate through facial expressions and by making noises.
15. Thanks to modern irrigation， crops now grow abundantly inareasswheresonce nothing but cacti and sagebrush could live.
16. The development of mechanical timepieces spurred the search for moreaccurate sundials with which to regulate them.
17. Anthropology is a science in that anthropologists use a rigorous set ofmethods and techniques to document observations that can be checked byothers.
18. Fungi are important in the process of decay， which returns ingredientsto the soil， enhances soil fertility， and decomposes animal debris.
19. When it is struck， a tuning fork produces an almost pure tone，retaining its pitch over a long period of time.
20. Although pecans are most plentiful in the southeastern part of theUnited States， they are found as far north as Ohio and Illinois.