The correct answer is: B. radial or star and block road pattern.
The Nagpur road plan formula was prepared by assuming a radial or star and block road pattern. This means that the city is divided into a number of sectors, each with its own radial road leading out from the city center. The sectors are then further divided into blocks, each with its own grid of streets. This type of road pattern is efficient for moving traffic around the city, and it also provides a good level of access to different parts of the city.
The other options are incorrect because they do not accurately reflect the road pattern in Nagpur. Option A, rectangular or block road pattern, is incorrect because the road pattern in Nagpur is not rectangular. Option C, radial or star and circular road pattern, is incorrect because the road pattern in Nagpur does not include circular roads. Option D, radial or star and grid road pattern, is incorrect because the road pattern in Nagpur does not include a grid of streets.