Solution:Under Article 352, the President can declare a national emergency when the security of India or a part of it is threatened by war or external aggression or armed rebellion.
The president may proclaim a national emergency if he considers there is an urgent danger of war, external aggression, or armed rebellion, even before any of these events actually occur.
Under Article 353 (B) State legislatures continue to operate and legislate, but parliament assumes concurrent legislative power on state subjects and a law such enacted by parliament, shall cease to operate at the expiry of six months after the revocation of national emergency, to the extent of incompetency.
If parliament approves such a proclamation, then it will be in force for 6 months from the date on which it was approved by the parliament, unless revoked earlier.