In What Sense Does the Problem of Littering Represent a Social

In what sense does the problem of littering represent a social dilemma?

A) Each citizen may not litter a lot, but it all adds up.
B) Littering has increased steadily over the last fifteen years.
C) People often look to one another to guide their behaviour.
D) Litter pollutes water and endangers wildlife.
E) Norms can be made salient to reduce littering.