Assume that a house is rented by four students. When it comes to keeping the house clean, each of the four roommates has an incentive to leave cleaning to the others. As a result, the house is never clean

Which of the following is the best solution to this problem of free riding?
A) Assign one roommate the responsibility to keep a watch over the other students
B) Require every roommate to contribute to a cleaning service
C) Ask every roommate to clean the house if they dirty it
D) Require each roommate to pay more toward the house rent and groceries

B