We must be extra vigilant, The government must play its role as to make the environment safe and remove all environmental factors cancer. (OMITTED) Good sources of drinking water, he says,will stop people from going to streams and ponds, where they get infected with some of these organisms.

VOA: standard.2010.06.16

The respiratory system plays an important role in maintaining our internal environment at the proper level of oxygen, by bringing the right amount in.

呼吸系统的重要性在于,通过向体内输入适量的氧气,维持人体内环境中的氧平衡

耶鲁公开课 - 生物医学工程探索课程节选

The respiratory system plays an important role in maintaining our internal environment at the proper level of oxygen, by bringing the right amount in.

呼吸系统的重要性在于,通过向体内输入适量的氧气,维持人体内环境中的氧平衡

耶鲁公开课 - 生物医学工程探索课程节选