Final answer:
The correct pronoun to use is "te" which means "to you"
Step-by-step explanation:
The correct pronoun to fill in the blank would be te. In this sentence, the subject is "A ti" which means "to you." The verb "gustan" means "you like," so the sentence translates to "You like plants." Therefore, the correct pronoun to use is the second person singular pronoun, which in this case is te.
Learn more about Pronouns in Spanish