Gandhiji supported decentralization of power because he believed that it was essential for the economic development of the country. Option 1, which suggests that decentralization ensures more participation of the people into democracy, is not mentioned as a reason for Gandhiji`s support. Option 2, which claims that India had decentralization of power in the past, is not relevant in explaining Gandhiji`s support for decentralization. Option 4, which states that decentralization can prevent something (information missing), is incomplete and does not provide a clear reason for Gandhiji`s support. Therefore, the correct answer is option 3, which explains that Gandhiji believed decentralization was necessary for the economic development of the country.