Which of the following facts about Vedic literature are true?

A. Hiranyagarbha Sukt is an example of monotheism.

B. Paippalada Samhita is a branch or edition of Atharvaveda.

C. Aitareya Brahmana tells us about systems of governance which were prevailed in later Vedic age.

D. Shatapath Brahmana tells us about the eastward expension of Aryans.

Mark the right answer.