the answer is “b. me divierto” because it is present tense. in english this means “I’m having fun”.
your sentence means “When I go out with Miguel, I always...” the answer is have fun, which means the answer is letter b.
here’s what each answer means:
a. me diverti - i had fun
b. me divierto - i have fun
c. me divertia - i used to have fun/i had fun
d. me divertiré - i will have fun/i’m going to have fun
i hope this helped :)