15. A. to visit
The correct answer is "to visit" because it indicates the intention or purpose of the person. "He'd like to visit the Louvre museum with his family this weekend."
16. B. feeding
The correct answer is "feeding" because it describes the action that Mr Long adores. "Mr Long adores feeding dogs with fish in the morning."
17. B. treating
The correct answer is "treating" because it describes the action of treating someone like a small kid. "He is 18 years old now. He hates being treated like a small kid."
18. C. staying - to stay
The correct answer is "staying - to stay" because it indicates Mr Long's preference. "In Summer, Mr Long would prefer staying with local people rather than staying in a five-star hotel."
19. B. keen
The correct answer is "keen" because it means having a strong interest or enthusiasm. "Mono is keen on chatting with Mr Long at the weekend."
20. B. go to the cinema - visit the museum
The correct answer is "go to the cinema - visit the museum" because it is the correct form of the verb after "rather than." "In my free time, I would rather go to the cinema than visit the museum."