Explanation: The question involves three statements related to geopolitical and historical aspects of South Asia. Let's analyze each statement in detail:
1. **Indo Bangladesh passports are valid to travelling to Sri Lanka and Bangladesh**: This statement is true. The Indo-Bangladesh passport, also known as the Bangladeshi passport, is a travel document issued by the Government of Bangladesh. It allows its holders to travel to various countries, including Sri Lanka and Bangladesh. This reflects the bilateral agreements and the ease of travel between these South Asian nations.
2. **India, Pakistan, Nepal, Bhutan, Bangladesh, and Sri Lanka form a subcontinent**: This statement is also true. These countries are collectively known as the South Asian subcontinent. The term "subcontinent" refers to a large, distinct geographical region that is part of a larger continent. South Asia is a subregion of the Asian continent, characterized by its unique cultural, linguistic, and geographical features. The countries mentioned share a common history, cultural heritage, and often face similar socio-economic challenges.
3. **After the East India Company became Diwan, peasants in Bengal were unable to pay the dues that were being demanded from them**: This statement is true and reflects a significant historical event. The East India Company became the Diwan (revenue collector) of Bengal in 1765 after the Battle of Buxar. The Company's rule was marked by heavy taxation and economic exploitation. The peasants in Bengal were subjected to exorbitant land taxes, which they often could not afford, leading to widespread poverty and famine. This period is often associated with the Bengal Famine of 1770, which resulted in the deaths of millions of people.
In conclusion, all three statements are true, making option C the correct answer. Understanding these statements requires knowledge of South Asian geopolitics, historical events, and the economic conditions of the past. This question highlights the interconnectedness of these aspects and their significance in the context of South Asian history and contemporary relations.