1-) El novio de mi prima se desenamoró de ella
2-) Mi ex novio se desenamoró de mi cuando le fuí infiel
3-) Yo me desenamoro muy rapido
Actually the answer is B.
Because nueve is 9 and nueve y cuarenta is 9:40, ocho y treinta is 8:30 which are the hours in the dialogue
What is this..I would like to help you on this.