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.