Correct Option: C

One of the observatories established by Sawai Jai singh was of Ujjain. The idea behind building a number of observatories at different locations in the northern India was to make the same observations from different places and thus reduce the errors introduced due to the limits of resolution of human vision. Sawai Jai Singh built the three small ones at Ujjain, Mathura, and Banaras with the help of Hindu astronomers who themselves had limitations in civil engineering (architectural engineering).