1) It happens when there's no rain for a long time a) b) 2) It happens when there's too much rainfall a) b) 3) It happens because the Earth's atmosphere is polluted a) b) 4) It can happen because of men's activities and wars  a) b) 5) It's in our atmosphere to protect us from radiation a) b) 6) It's the reason of pollution a) b)

The environment

列印
嵌入

排行榜

視覺風格

選項

切換範本

恢復自動保存: ?