Mi abuelo insiste que nosotros dormimos en su cuarto mientras visitamos la casa.

dormemos
durmamos
duermamos
duermemos

Duermemeos

Explanation:

First to solve this question you have to know what the sentence means and it means My grandfather insists that we sleep in his room while we visit the house. So now that we know what the sentence means we will use process of elimination to cancel out all of the wrong answers.

So you just have to look at each one and basically know what they mean. So dormemos means let's sleep durmamos also means let's sleep and duermamos also means let's sleep, but the word duermemos means we sleep so the only logical answer to this problem is duermemos.