Exp) option d is the correct answer.

The Constitution was framed by the Constituent Assembly of India, established by the members of the provincial assemblies elected by the people of India.

Dr Sachidanand Sinha, who was the oldest member of the assembly, was elected as the temporary chairman of the assembly, following the French Practice. Later, Dr Rajendra Prasad was elected its president.

Dr BR Ambedkar was the chairman of its Drafting Committee.

Source:

1. Indian Polity by Laxmikanth – Chapter Making of the Indian Constitution

2.https://eoi.gov.in/eoisearch/MyPrint.php?4645?000/0001#:~:text=Dr%20Sachidanand%20Sinha%20was%20the,Prasad%20was%20elected%20its%20president,%20lakshmikant