The correct answer is option 1, Dutch.

Indonesia was indeed a colony of the Dutch. During the 16th century, the Dutch established trading posts in the Indonesian archipelago, primarily for the lucrative spice trade. Over time, these trading posts expanded into a colonial empire. The Dutch East Indies, as it was called, was under Dutch control for more than three centuries, from the 17th century until Indonesia`s independence in 1945.

Options 2, 3, and 4 are incorrect. While Spain, Portugal, and Belgium were all European colonial powers during the Age of Exploration, none of them colonized Indonesia. Spain focused primarily on colonizing the Americas and parts of Asia, Portugal established colonies in places like Brazil and parts of Africa, and Belgium primarily colonized the Congo in Africa.