Definition: a form of oxygen that exists high in the atmosphere Level: C1
科学家们对臭氧层的变薄感到担忧。
Scientists are concerned about the thinning of the ___ozone layer.
臭氧层的消耗是一个严重的环境问题。
The depletion of the ___ozone layer is a serious environmental issue.
《蒙特利尔议定书》的制定是为了保护臭氧层。
The Montreal Protocol was enacted to protect the ___ozone layer.
