In which part of a house would you most likely have a barbeque?

a. el dormitorio
b. la terraza
c. el ático
d. el sótano

option B, La terraza.

Explanation: Let's analyze the options:

A "el dormitorio" means "the bedroom", this is not a nice place to do a barbeque, so we can discard this option.

B "La terraza" this means "the terrace", this is a good place, because the smoke can flow.

C "el atico" this means "the penthouse", this also is a bad place because you will fill the penthouse with smoke.

D "el sotano", means "the basement", this has the same problem as before.

So the only option tath makes sense, is the option B, La terraza.