An (ozone layer) may undergo a depletion.Logical formLearned from640 sentences. An (ozone layer) may pertain-to the earth.Logical formLearned from548 sentences. An (ozone layer) can be protective.Logical formLearned from487 sentences. Levels can be constituted-of-or-filled-with ozone.Logical formLearned from413 sentences. A hole can be in an (ozone layer).Logical formLearned from370 sentences. Ozone may undergo a formation.Logical formLearned from296 sentences. Holes can be in an ozone.Logical formLearned from290 sentences. An (ozone layer) may undergo destruction.Logical formLearned from267 sentences. Ozone may undergo concentrations.Logical formLearned from224 sentences. A hole can be in an (ozone layer).Logical formLearned from198 sentences. An (ozone layer) may undergo protection.Logical formLearned from192 sentences. Ozone may undergo destruction.Logical formLearned from182 sentences. An (ozone layer) may undergo thinnings.Logical formLearned from167 sentences. Ozone may undergo a depletion.Logical formLearned from166 sentences. (Ozone levels) can be high.Logical formLearned from161 sentences.