The option that is NOT one of the new military methods that allowed Rome to conquer all of Italy and achieve the first political unification of the peninsula is Plebeian uprising.
The plebeian uprisings were social and political movements aimed at increasing the rights and power of the plebeians (the common people) in Rome, rather than military methods used for conquest. The other options (the javelin, cavalry, and organized infantry) refer to specific military strategies and tactics.