The current period of global warming that Earth is undergoing is caused by certain gases in the atmosphere,notably carbon dioxide. 現在地球正經歷的全球暖化是由大氣層中天然氣所引起,尤其是二氧化碳 這種同一句出現兩個is 常常會突然間看不懂耶... 這是什麼文法阿?
that Earth is undergoing 是用來形容global warning的這句的主詞是global warning,第二個is才是主要的be動詞結構其實就解讀為 global warning is caused by...什麼樣的global warning呢? that Earth is undergoing這坨叫做子句,想成是依附在global warning下類似形容詞的東西二樓沒必要那麼不客氣吧,不屑回答就別回,人家問得很誠肯