他们进行了一项为期五年的关于野生动物与农业关系的研究。

They conducted a five-year ___study of the relationship between wildlife and farming.

一些研究表明某些类型的人工甜味剂与癌症之间存在联系。

Some ___studies have suggested a link between certain types of artificial sweetener and cancer.

但是，正如科学家们最近的一项研究所显示，臭氧层日益减少也归因于所有私家车产生的排放。

But, as a recent ___study by scientists has shown, the growing lack of ozone is also due to the emissions produced by all the private cars.