If definite articles are used on the subject of a sentence, why are they used with ríos and vegetación? Isn't the subject of the sentence acid rain? If a word that receives the action of the verb (contaminar) is the object , doesn't that make ríos and vegetación objects not subjects?
I think I've reached the limit of all my understanding of grammar in both Spanish and English. I can't get this right. I'm ready to quit.