The correct answer is option 4: Internal disturbance. According to the Constitution of India, the President can proclaim a state of Emergency on the grounds of war, armed rebellion, or external aggression. However, internal disturbance is not considered a ground for the proclamation of Emergency.

War refers to a state of conflict between nations, while armed rebellion refers to an uprising against the government using weapons. External aggression refers to an attack on India by a foreign nation or entity. These three situations are considered severe threats to the security and stability of the country and can warrant the declaration of Emergency.

On the other hand, internal disturbance refers to civil unrest, protests, or other forms of unrest within the country. While internal disturbance can pose challenges to governance, it does not meet the level of severity required for the proclamation of Emergency.