Answer:
b. 251 to 500
Explanation:
The Ganges plain in India is a heavily populated region of the planet. The primary reason for the high population densities in this region is related to its suitability for agriculture and adequate presence of water. Population densities of 1000 per square mile is reported for this region. Converting this figure to number of people per square km , we need to divide the value by 2.59. This yields a value in the range 251 to 500. So b is the required option.