為何現在式的另一個動詞要加ed

Fuel oil is a fraction obtained from petroleum distillation

請問各位大大,水水

為什麼這一個句子中的另一個動詞obtained要加ed
更新: Fuel oil is a fraction which is obtained from petroleum distillation.

那請問這一句

為何不能寫成

Fuel oil is a fraction which is obtain from petroleum distillation

???
更新 2: 再請問一下

像這句

Distillate fuel oils are distilled form curde oil.

為何後面的動詞也要加ed

還是distilled在此是當形容詞呢>>>???
2 個解答 2