Answer:
The answer is: letter c, a recycling program
Explanation:
A "free-rider" problem happens when <em>some members in the society don't contribute an equal share in the cost of a shared resource. </em>
Among the choices above, the recycling program will give rise to such situation. For example, when it comes to a recycling program of making a school's wall out of recycled bottles (in order to protect it from outsiders), not everyone will join the program yet, most of the time, the program is done for the good of the society. In this case, for the good of the school and the people visiting it.
This results to many free riders taking advantage of the school's wall, including the people who visits the school (parents, babysitters, friends, guardians etc.) and loiters in the area to pass time while waiting for their kids or friends
