In many countries, it is possible to buy and use a special device that will warn when harmful levels of carbon monoxide are in the area.

VOA: special.2010.02.02

It's a common bacterium and most strains of E. Coli are not harmful to people, in fact, they provide us with some beneficial properties.

它是常见菌,且大多数种类的菌株对人类无害,实际上还给了我们颇多裨益

耶鲁公开课 - 生物医学工程探索课程节选

It's a common bacterium and most strains of E. Coli are not harmful to people, in fact, they provide us with some beneficial properties.

它是常见菌,且大多数种类的菌株对人类无害,实际上还给了我们颇多裨益

耶鲁公开课 - 生物医学工程探索课程节选