Concept:The correct phrasal verb is “make it up to,” which means to apologise to someone or compensate them after doing something wrong.Explanation:After a quarrel, a person usually wants to repair the relationship with the other person.The expression “make it up to his friend” means he will apologise or do something good to make amends.The word “up” completes the phrasal verb correctly.Answer:D. upAfter the quarrel, he made it up to his friend.