You observe one of your close friends is often unfair with you. You will

The correct choice is: tell your friend how you feel and that this situation is not acceptable to you.

In a close friendship, problems should be discussed openly and honestly.

Telling your friend how you feel and that his behaviour is not acceptable gives him a chance to change. Gossiping, avoiding him, or silently hoping he realises his mistake does not solve the problem.

Hence the best response is ‘tell your friend how you feel and that this situation is not acceptable to you.’