Identifying: What factors might explain why western China is less densely populated than eastern China?

China’s complex natural conditions have produced an unevenly distributed population. Population density varies strikingly, with the greatest contrast occurring between the eastern half of China and the lands of the west and the northwest.

Explanation:

a is the final ! : )

an informal structure in a bureaucracy would be something like so-called "office politics". where there's a formal structure set up for the organization, but then an informal subculture as well that has a way of organizing the bureaucracy further. this can be positive because it sets up an added degree of organization, albeit informal, within the bureaucracy.