In which ancient Scripture was the phrase "Tamaso Ma Jyotirgamaya" originally mentioned?

Which of the following Rig-Vedic Gods is not mentioned in 'Boghazkoi' inscription?

In which Upanishad is the famous dialogue of Yagnavalkya and Gargi mentioned?

Which of the following inscriptions tells about the Aryan’s movement of Aryan from Iran to India?

The river mentioned most in early Vedic literature is :

Which of the following rivers mentioned in the Rig Veda indicates the relations of Aryans with Afghanistan?