Concept:
Migraine prophylaxis is used when attacks are frequent or disabling. Beta blockers such as propranolol are commonly used for migraine prevention.
Step 1: Differentiate acute treatment and prophylaxis.
Sumatriptan is used for acute migraine attacks. Prophylaxis requires drugs such as beta blockers, topiramate, or valproate.
Step 2: Identify the best option.
Among the given options, propranolol is a standard migraine prophylactic drug.
Step 3: Avoid acute-only drugs.
Ergotamine and naratriptan are mainly used for acute migraine treatment, not routine prophylaxis.
Therefore, the correct answer is Propranolol.