Here it states which element will possess the most valence electrons. Now one of them I already gave away. Remember aluminum is in Group 3A, so it has three valence electrons.
Now if we look, we have sulfur, calcium, hydrogen and bromine. None of them are transition metals. So we don't have to worry about the number of S or D electrons that they possess. They're all main group elements.
So look on your periodic table and see what group do they belong to. Sulfur is in Group 6A, so it has six valence. Calcium is in Group two ways, so it has two valence electrons. Hydrogen is in Group 1A, so it has one valence electrons, and then finally bromine is in Group 7A, so it has seven valence electrons.
So we'd see that bromine is the one that has the most valence electrons at 7:00.