As a multiple choice question, you could make an argument for either choice (a) one, or choice (d) seven. See the discussion below.
Bromine generally forms only one covalent bond, consistent with the fact that only one of its seven valence electrons is unpaired.
It does have other oxidation states which appear when it bonds to more electronegative elements like F or Cl, but these are much less common than the -1 state that is seen in its bonds with most elements.
That said, one could also make the point that bromine does have seven valence electrons, and there are cases in which all seven are involved in bonding. So, it is a bit of a tough call in a multiple-choice situation. I would ask for clarification on the question if possible!