The Brahma Samaj is based on the principle of

Monotheism
Polytheism
Atheism
Monism

The correct answer is (d) Monism.

Brahma Samaj is a Hindu reform movement founded in 1828 by Raja Ram Mohan Roy. It is based on the principle of monism, which is the belief that there is only one ultimate reality. This reality is Brahman, which is both the material and spiritual world. Brahman is impersonal and unknowable, but it can be experienced through meditation and devotion.

Monotheism is the belief in one God. Polytheism is the belief in many gods. Atheism is the belief that there is no God.

Brahma Samaj rejects the caste system and idol worship. It promotes education and social reform. It has been influential in the development of modern Hinduism.