**Explanation:**

The correct answer is option 'B' - Constituent Assembly.

**Constituent Assembly:**
The Constitution of India was framed by the Constituent Assembly. The Constituent Assembly was a body of representatives elected by the people of India to draft and adopt a new constitution for the country. It was formed on 9th December 1946, and its members were chosen by indirect election by the members of the provincial assemblies. The total strength of the Constituent Assembly was 389 members.

**Role of the Constituent Assembly:**
1. Drafting the Constitution: The primary responsibility of the Constituent Assembly was to draft the Constitution of India. It deliberated on various issues, discussed different provisions, and ultimately framed the Constitution.
2. Debates and Discussions: The Constituent Assembly held several debates and discussions on various aspects of the Constitution, including fundamental rights, directive principles of state policy, system of government, etc. These debates helped in shaping the final provisions of the Constitution.
3. Committee Formation: The Constituent Assembly formed several committees to assist in the drafting process. These committees, such as the Drafting Committee, Steering Committee, and various sub-committees, played a vital role in formulating and finalizing the constitutional provisions.
4. Amending and Finalizing the Draft: The Constituent Assembly reviewed and amended the draft constitution several times during its deliberations. It considered the suggestions and recommendations put forth by its members and incorporated them into the final draft.
5. Adoption of the Constitution: After several years of intense debates, discussions, and revisions, the Constituent Assembly adopted the Constitution on 26th November 1949. This day is celebrated as Constitution Day or National Law Day in India.

**Conclusion:**
The Constitution of India was not framed by the Planning Commission, President, or Working Committee. It was the Constituent Assembly that undertook the monumental task of drafting and adopting the Constitution. The Constituent Assembly ensured the representation of diverse voices and perspectives from across the country, and its efforts resulted in the creation of a comprehensive and democratic framework for the governance of India.