For example,animal waste and cattle digestive systems release methane gas.

VOA: special.2010.01.05

The respiratory system, for example, the renal system, the digestive system, these are examples - three examples of organ systems that contact the external environment.

例如,呼吸系统,泌尿系统,消化系统,这些系统,这三个系统,与外环境相联系

耶鲁公开课 - 生物医学工程探索课程节选