Some examples of possibilities:
You are playing with your friends and someone you don’t usually play with asks if they can join the group.
You are in a group with your friends and your best friend makes an off handed joke about someone’s size. You can tell through body language that it really hurt the person’s feelings, but they didn’t say anything. What do you do or say?
You have one friend who insists they want to spend time only with you next recess. You have other friends who you would equally like to spend time with, what do you do?