The correct answer is option 4: when the decision of the Union Cabinet for the issue of such proclamation has been communicated to him in writing.

The President of India has the power to issue a proclamation of Emergency under Article 352 of the Indian Constitution. However, this power is not absolute and can only be exercised under specific circumstances.

According to the Constitution, the President can declare an Emergency when the Union Cabinet, which consists of the Prime Minister and other ministers, has made a decision to issue such a proclamation and has communicated it to the President in writing. This means that the President cannot unilaterally decide to issue an Emergency proclamation; it must be based on the collective decision of the Council of Ministers.

Options 1 and 2 are not correct because they suggest that the President can only issue a proclamation of Emergency on the advice of the Prime Minister or the Council of Ministers. While the advice of the Prime Minister and the Council of Ministers may be taken into consideration, the decision ultimately lies with the President.

Option 3 is also not correct because it states that the President can issue a proclamation of Emergency in his own discretion without any reference to the Council of Ministers. This is not true as the President`s power to declare an Emergency is limited and subject to the decision