The correct answer is option 4: 1870.

Option 1: 1884 - This is not the correct answer.

Option 2: 1876 - This is not the correct answer.

Option 3: 1869 - This is not the correct answer.

The Poona Sarvajanik Sabha was established in the year 1870. The Poona Sarvajanik Sabha was one of the earliest social and political organizations in India. It was founded by scholars and social reformers from Pune, Maharashtra, with the aim of working towards social and educational reform in the country.

The organization played a crucial role in advocating for the rights and welfare of the marginalized sections of society. It actively worked towards the abolition of untouchability, promotion of women`s education, and upliftment of the lower castes. The Poona Sarvajanik Sabha organized various public meetings and conferences to raise awareness about social issues and bring about positive change in society.

Therefore, the correct answer is option 4: 1870.