To live a happy life,we must take some measures to prevent pollution ___it is too late
问题描述：
To live a happy life,we must take some measures to prevent pollution ___it is too late
A、since B、when C、once D、 before
答
To live a happy life,we must take some measures to prevent pollution before it is too late
要过上幸福的生活,我们必须采取措施,防止污染,要不就太迟了