The holy Hindu scriptures written by gurus to help connect people to heavenly forces are primarily the Upanishads and the Mahabharata (which includes the Bhagavad Gita, a sacred text). The Ramayana is also a revered epic in Hinduism but does not traditionally fall under the category of scriptures written by "gurus" in the same sense as the Upanishads and the Mahabharata. "Theravada" refers to a branch of Buddhism, not Hindu scriptures.
So, the correct responses among those listed are:
- the Upanishads
- the Mahabharata
- the Ramayana (though it is less directly associated with the concept of connecting to heavenly forces through the teachings of gurus compared to the other two).
If you have to choose the primary ones, go with the Upanishads and the Mahabharata.