Which One of the Following Is the Best Example of a Mediated

Which one of the following is the best example of a mediated learning experience?

A) Mr. O'Brien insists that students sit quietly at their desks before she dismisses them for lunch.
B) Mr. James reflects on the lesson he taught earlier in the day. "I suspect that most of my students still don't understand the concepts I was trying to teach them," he thinks.
C) Mr. Lucas asks his students to read Chapter 5 in their textbooks over the weekend. "You'll find that the chapter is more challenging than previous ones," he says.
D) As Ms. Robinson takes a group of children hiking, she gathers leaves from maple, oak, and elm trees and points out the ways in which the leaves from the trees are distinctly different.