The first monarch of Magadh kingdom in the sixth century B.C. was
The correct option is A. Bimbisara
Bimbisara, (born c. 543—died 491 BCE), one of the early kings of the Indian kingdom of Magadha. His expansion of the kingdom, especially his annexation of the kingdom of Anga to the east, is considered to have laid the foundations for the later expansion of the Mauryan empire. He is also known for his cultural achievements and was a great friend and protector of the Buddha.