The three correct answers regarding the significance of the Vedas are:
- They contributed to the development of Hinduism.
- They show the history of the Indo-Aryans.
- They are used in Hindu rituals today.
(Note: The Vedas are not considered the world's longest poem, and they have been written down, though they originated as oral traditions. They also introduce the concept of Brahman, but that wasn't listed as one of the requested correct answers).