The War Fought in Spain Was Significant Because It

The war fought in Spain was significant because it:

A) proved once and for all the invincibility of Napoleon's battlefield tactics.
B) indicated that Napoleon could be defeated militarily.
C) finally allowed Spain and Portugal to be reunified into a single country.
D) was the means to forge the Fourth Coalition to finally defeat Napoleon.
E) showed the superiority of French rifles and artillery over that of the Spanish.