The amount of precipitation on a given day is an example of
a. climate
b. latitude
c. rain fall
d. weather

It would be C because the precipitation is the rainfall. But all this plays into the climate so the answer could also be A. I would go with  C though

C, because due to rain fall, precipitation is given at the same action of a rain fall.

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.