The index of modernisation is ___________.
The index of modernisation is not a decrease in the number of cities. Nor, it is the decrease in the number of towns. Also, the growing population in rural areas affect the health and well-being of the people residing at the place. This all affects the development and thus not depict modernisation. However, the stable population in rural areas lead to better education and health facilities and a decrease in mortality rates. Thus, an index of modernisation.
Thus, the correct answer is D.