Answer:
3. We formed the club because you are able to trade tips with other gardeners.
Step-by-step explanation:
An antecedent is a word, phrase or clause that a pronoun refers to. In sentence number 3, there is an error in pronoun-antecedent agreement because the pronoun "you" does not match its antecedent "We", and it leaves room for doubt and confusion. To fix the error, you should replace the pronoun "you" with "we".