The correct answer is option 'D' - Dadabhai Naoroji.

The Congress Session at Calcutta in 1906 was a significant event in the history of the Indian National Congress. It marked a turning point in the organization's approach towards the fight for independence and laid the groundwork for future political movements.

Here are the details explaining why Dadabhai Naoroji presided over the Congress Session at Calcutta in 1906:

1. Dadabhai Naoroji:
- Dadabhai Naoroji was one of the prominent leaders of the Indian National Congress and is often referred to as the "Grand Old Man of India."
- He was a staunch advocate for the rights of Indians and played a crucial role in shaping the early nationalist movement.
- Naoroji was the first Indian to be elected to the British Parliament and was a strong voice against British colonial rule.
- He was known for his economic critique of British policies, particularly the drain of wealth from India to Britain.
- His presidency at the Calcutta session in 1906 was significant as it reflected the growing influence of moderate leaders within the Congress who aimed for constitutional reforms and dialogue with the British rulers.

2. The Calcutta Session of 1906:
- The Congress Session at Calcutta in 1906 was a turning point for the Indian National Congress.
- It witnessed the emergence of the 'moderate' faction of the Congress, which advocated for reforms within the framework of British rule.
- The session saw the emergence of leaders like Gopal Krishna Gokhle, Surendranath Banerjee, and Dadabhai Naoroji who aimed to work with the British government to secure political and social reforms.
- Dadabhai Naoroji presided over this session, which further strengthened his influence and position within the Congress.

In conclusion, Dadabhai Naoroji presided over the Congress Session at Calcutta in 1906. His presidency marked the emergence of the moderate faction within the Congress and their approach towards seeking reforms within the British colonial framework.