President can declare an emergency in India when:

When the council of ministers sends a request to him in writing

The correct answer is Option (4) - When the council of ministers sends a request to him in writing

Lessons learnt from the 1975 National Emergency:

The Emergency at once brought out both the weaknesses and the strengths of India’s democracy. Though there are many observers who think that India ceased to be democratic during the Emergency, it is noteworthy that normal democratic functioning resumed within a short span of time.

One lesson of Emergency is that it is extremely difficult to do away with democracy in India.

Secondly, it brought out some ambiguities regarding the Emergency provision in the Constitution that have been rectified since. Now, ‘internal’ Emergency can be proclaimed only on the grounds of ‘armed rebellion’ and it is necessary that the advice to the President to proclaim Emergency must be given in writing by the Council of Ministers.

Thirdly, the Emergency made everyone more aware of the value of civil liberties. The Courts too, have taken an active role after the Emergency in protecting the civil liberties of the individuals. This is a response to the inability of the judiciary to protect civil liberties effectively during the emergency. Many civil liberties organisations came up after this experience.