Marco accepts a request to play the piano at his church's sunday services, even though he is still learning how to play the piano. he plays a well-learned, simple piece. happily, he performs very well in front of his congregation. marco's behavior illustrates

Social facilitation

Explanation:

Social facilitation is a concept where the presence of other people increases an individual's performance of a skill or ability. Many approaches have been used to study this in psychology, such as the activation theory.

The activation theory believes that the presence of other people would only benefit the individual if they are performing simple tasks that they have mastery over - if the individual is instead performing unfamiliar and complex tasks, performance would instead be negatively affected.

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.