科学家不知道为什么恐龙灭绝，但是有些理论假定了地理、气候、海平面的改变是对恐龙的灭绝有影响的。
Scientists do not know why dinosaurs became extinct,but some theries postulate that changers in geography,climate,and sea levels were responsible.
园艺科技从其他自然科学利用资源，他们关注的是最多的收益和最高的质量。
The science of horticulture,in which the primary concerns are maximum yield and superior quality,utilizes information derived from other sciences.
雪能保持表层土壤的温度以帮助农民，从而挽救种子不被冰冻。
Snow aids farmers by keeping heat in the lower ground levels,thereby saving the seeds from freezing.
