Option 1 - Nagaland: Nagaland has not seen a series of strong public protests against the Armed Forces Special Powers Act (AFSPA) in force in the state. It has had a history of insurgency movements and demands for independence, but protests specifically against AFSPA have been more prominent in other states.

Option 2 - Manipur: Manipur is the correct answer. The state has witnessed a series of strong public protests against AFSPA. AFSPA gives the armed forces special powers to maintain law and order in disturbed areas, but it has been a topic of controversy due to allegations of human rights abuses by security forces in Manipur.

Option 3 - Jammu and Kashmir: Jammu and Kashmir has seen protests against AFSPA, but not as consistently and prominently as Manipur. The state has its own separate legislation known as the Armed Forces (Jammu and Kashmir) Special Powers Act.

Option 4 - Jharkhand: Jharkhand has not experienced strong public protests against AFSPA. The state does not have AFSPA in force, as it is primarily applicable to areas affected by insurgency and not prevalent in Jharkhand.

In summary, Manipur is the correct answer as it has seen a series of strong public protests against AFSPA.