大学英语：It has its obscure and unpretentious beginning

15. It has its obscure and unpretentious beginning; its quite stretches as well as its rapids; its periods of drought as well as of fullness.

其源头，隐隐约约，并不引人注目;其流势,时而平缓,时而湍急;其水情, 有汛期,也有枯谒期.

16. Dr. Knipling was ready for a full-scale test of his theory.

尼普林教授已在佛罗里达岛进行了一些实地预备性实验, 并计划大规模地实践其理论.

17. the resounding success of the Curacao experiment whetted the appetities of Florida livestock raisers for a similar feat that whould relieve them of the scourge of screw-worms.

库拉索岛上的实验大获成功. 这引起了佛罗里达州特征畜饲养者的兴趣,他们希望借助这一成果帮他们摆脱螺旋铃绳这一祸害.

18. prearranged flight parents.

事先安排好的飞行队形.

19. 中国还对广阔的大陆架和专属经济区行使主权权利和管辖权;中国的海域处在中,低纬度地带,自然环境和资源条件比较优越. 人工养殖.

China also exercises sovereignty and jurisdiction over the vast continental shelves and exclusive economic zone, as defined by the Un Convention on the Law of the Sea. Located in medium and low latitudes, China’s sea areas have comparatively advantageous natural environmental and resource conditions