Introduction:
The Diwan of Bengal was responsible for collecting revenues in the region. In this case, the Diwan belonged to the East India Company. Let's explore the details.

Explanation:
1. East India Company:
The East India Company was a British trading company that had established its presence in India during the 17th century. It gradually gained control over various regions in India, including Bengal. The company operated as a commercial entity but also had political and administrative powers granted by the British government.

2. Bengal under East India Company:
After gaining control over Bengal, the East India Company implemented several administrative changes in the region. The Company appointed its officials to key positions and introduced reforms to streamline the collection of revenues. The Diwan was one such important position responsible for revenue administration.

3. Role of the Diwan:
The Diwan played a crucial role in the revenue administration of Bengal. They were responsible for collecting taxes, maintaining records, and ensuring the efficient collection of revenues. The Diwan worked under the authority of the East India Company and implemented the revenue policies of the Company.

4. Importance of Revenue Collection:
Revenues collected from Bengal were vital for the East India Company. Bengal was a wealthy and prosperous region, known for its agricultural productivity and trade. The revenue collected from Bengal helped finance the Company's activities, including trade, military expeditions, and administrative expenses.

5. Other Options:
a) Mir Qasim: Mir Qasim was the Nawab of Bengal in the mid-18th century. He rebelled against the East India Company's policies and formed an alliance with other regional powers. While he did introduce certain reforms during his reign, he did not collect revenues for the Company.

b) Warren Hastings: Warren Hastings was the first Governor-General of Bengal appointed by the British government in 1773. While he played a significant role in the administrative and judicial reforms of Bengal, he did not directly collect revenues as the Diwan.

c) None of these: This option is incorrect as the correct answer is option 'A', which is the East India Company.

Conclusion:
In conclusion, the Diwan responsible for collecting revenues in Bengal during the mentioned period belonged to the East India Company. The Company's control over Bengal allowed it to implement revenue administration policies and utilize the collected revenues for its own purposes.