The correct answer is (d) 1885.
Dehradun was connected to the railway network in 1885, when the Dehradun Railway Station was opened. The station was built by the British government as part of the North-Western Railway. It is located in the city of Dehradun, in the Indian state of Uttarakhand. The station is a major railway junction, and is served by trains from all over India.
The other options are incorrect. Option (a) is incorrect because the Dehradun Railway Station was not opened in 1910. Option (b) is incorrect because the Dehradun Railway Station was not opened in 1900. Option (c) is incorrect because the Dehradun Railway Station was not opened in 189.