Bhowali Sanitorium of district Nainital was established in the year _____.

The correct answer is (b) 1912.

Bhowali Sanatorium is a hill station in the Kumaon region of Uttarakhand, India. It is located at an altitude of 2,205 metres (7,234 ft) above sea level, on the southern slopes of the Himalayas. The sanatorium was established in 1912 by the British Raj as a sanatorium for patients suffering from tuberculosis. It is now a popular tourist destination.

The other options are incorrect. Option (a) is incorrect because Bhowali Sanatorium was established in 1912, not 1890. Option (c) is incorrect because Bhowali Sanatorium was established in 1912, not 1918. Option (d) is incorrect because Bhowali Sanatorium was established in 1912, not 1921.