Salvador Dalí era un pintor

Hola Ελισάβετ 

In this sort of text (biography type) it is more common to say " ...... era ..." because even though the person is dead, what we mean here is "this person used to be..."and it also have more of a descriptive function.

We could have also used "fue", of course, that would have also been correct (so we will add that sentence as another correct option in this exercise). If we say "fue" we then see this more as something with an end, not so much as a descriptive verb.

I hope this helped.

Inma