On the first day of class, professor everitt tells her psychology students that pop quizzes will be given at unpredictable times throughout the semester. studying for professor everitt's surprise quizzes will be reinforced which type of schedule?

The answer is "variable-interval schedule".

In operant conditioning, a variable-interval schedule is a schedule of support where a reaction is compensated after an eccentric measure of time has passed. This timetable delivers a moderate, consistent rate of reaction. As you likely review, operant conditioning can either fortify or debilitate practices using support and discipline. 

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.