Answer:
Fortunato insulted Montresor about not doing good in school and life.
Montresor stopped being friends with Fortunato because all the insults he received.
Fortunato still considered Montresor a friend, but not an important one, even though he would always insult him.
Montresor was truly angry with this, that he lured Fortunato into a catacomb where he keeps his wine under his house and left him to die.
Step-by-step explanation: