The correct answer is Option 4: it was an instance of Conference held in three sessions and not that of three separate conferences.

The meeting of Indian and British political leaders during 1930-32 in London is commonly referred to as the First, Second, and Third Round Table Conferences. However, it would be incorrect to label them as separate conferences due to the following reasons:

1. The Indian National Congress did not take part in two of them (Option 1): The Indian National Congress, the largest political party representing the Indian independence movement at that time, decided to boycott the Second Round Table Conference held in 1931. The Congress believed that the British government`s proposals did not adequately address their demands for self-rule and representation. Therefore, referring to these meetings as separate conferences implies a level of participation from the Indian National Congress that did not exist for the Second Round Table Conference.

2. Indian parties other than the Indian National Congress participating in the Conference represented sectional interests and not the whole of India (Option 2): While some Indian political parties other than the Indian National Congress did participate in the Round Table Conferences, their representation was limited and did not encompass the entirety of Indian interests. These parties often represented specific communities or sectional interests rather than representing the entire Indian population. Therefore, labeling them as distinct conferences may create the misconception that they were comprehensive in representing Indian aspirations as a whole.

3. The British Labour Party had withdrawn from the Conference, thereby making the proceedings of the Conference partisan (Option 3): The British Labour Party, which was sympathetic to Indian self-rule, withdrew from the Second Round Table Conference due to disagreements with the Conservative-led government`s handling of the Indian political situation. The withdrawal of the Labour Party meant that the proceedings of the conference became more partisan and did not have the balanced representation and bipartisan approach that was intended. This further undermines the notion that the conferences were separate and distinct.

4. It was an instance of a conference held in three sessions and not that of three separate conferences (Option 4): The Round Table Conferences were a series of meetings held in three sessions in London from 1930 to 1932. The purpose of these conferences was to discuss constitutional reforms for India and find a mutually agreeable solution between Indian leaders and the British government. While there were breaks between the sessions, they were intended to be part of an ongoing process of negotiation rather than separate and independent conferences.

In summary, referring to the meetings held during 1930-32 as the First, Second, and Third Round Table Conferences may create the misconception that they were separate and distinct events, when in fact they were part of an ongoing process held in three sessions. The absence of the Indian National Congress, the limited representation of Indian interests, and the partisan nature of the proceedings further highlight the need to view these meetings as a continuous process rather than separate conferences.