The reason for the resignations of the Indian ministers in all the provinces in the year 1939 was option 4 - India was declared a party to the Second World War without the consent of the provincial governments. This decision by the British government to involve India in the war without consulting the elected provincial governments was met with widespread opposition from Indian political leaders.

Option 1 - The governors refusing to act as constitutional heads was not the reason for the resignations. While the role of the governors was important in the events that unfolded, it was not the main cause.

Option 2 - The Centre not providing the required financial help to provinces was also not the reason for the resignations. While financial issues were a concern, the main reason was the declaration of India`s involvement in the war.

Option 3 - The Governor-General converting Indian administration from federal to unitary one because of the beginning of the Second World War was not the reason. While the war did have an impact on the governance structure, it was not the direct cause of the resignations.

It is important to note that the provided answer correctly states option 4 as the reason for the resignations. No alert is required.