The correct option is C Population density must be at least 400 people per sq km
A settlement has to fulfill certain criteria in order to be deemed as urban settlement. In India, a settlement is considered urban if it has a population of over 5000. The density of population must be at least 400 people per sq km. Also, at least 75% of the population must be involved in non-agricultural activities for a settlement to be called urban. Usually, administrative headquarters like municipalities, corporations, and military cantonments are all designated as urban centres.