M. N Roy ,Pioneer of the communist movement in India was the person who for the first time in 1934 put forward the idea of constituent Assembly for India.

The correct answer is option 'C', M.N. Roy.

M.N. Roy, also known as Manabendra Nath Roy, was an Indian revolutionary, politician, and philosopher. He played a significant role in the Indian independence movement and was one of the key proponents of the idea of a Constituent Assembly for India.

Here is a detailed explanation:

1. M.N. Roy's role in the Indian independence movement:
- M.N. Roy was actively involved in the Indian National Congress and the revolutionary movements against British colonial rule.
- He participated in various protests and agitations, advocating for complete independence from British rule.
- Roy was a founding member of the Hindustan Republican Association (HRA), later renamed the Hindustan Socialist Republican Association (HSRA), which aimed to overthrow British rule through armed struggle.

2. Introduction of the idea of a Constituent Assembly:
- M.N. Roy first put forward the idea of a Constituent Assembly for India in 1934.
- He proposed the establishment of a Constituent Assembly to frame a constitution for an independent India.
- Roy believed that a Constituent Assembly should consist of representatives elected by the people of India, who would draft a constitution reflecting the aspirations and values of the nation.

3. Significance of the idea:
- The concept of a Constituent Assembly gained significant importance as it provided a platform for Indians to decide their own destiny and shape the future of the country.
- It aimed to ensure a democratic and participatory process for drafting the constitution, allowing for diverse opinions and interests to be represented.
- The Constituent Assembly became a critical institution in post-independence India, responsible for formulating the Constitution of India, which was adopted in 1950.

In conclusion, M.N. Roy, a prominent figure in the Indian independence movement, proposed the idea of a Constituent Assembly for India in 1934. His vision for a democratic and representative body to draft the constitution played a crucial role in shaping the future of the nation.