Who among the following acted as the constitutional advisor to the Constituent Assembly?

Bhim Rao Ambedkar Sachidananda Sinha B N Rau Dr Rajendra Prasad

B N Rau

Sir Benegal Narsing Rau (26 February 1887 – 30 November 1953) was an Indian civil servant, jurist, diplomat, and statesman known for his key role in drafting the Constitution of India. He was the Constitutional Advisor to Constituent Assembly.