Reasoning: The word "it" is a pronoun because it refers to the weather. What is an antecedent? An antecedent is a noun or pronoun to which another noun or pronoun refers. It usually goes before the pronoun ("ante" means before).
I'm not sure if this is exactly correct, but to complete photosynthesis, plants need carbon dioxide and water. Usually sunlight as well. If you are supposed to be specific, you could put H2O. I hope I answered your question!
