The Free-Rider Problem Refers To

The free-rider problem refers to:

A) the situation in the Old West when land was largely unfenced and riders had unfettered access to private range land.
B) qualifications, or riders, that clients do not request, but which lawyers tend to include in contracts anyway.
C) a variation on the phrase "There's no such thing as a free lunch," which is replaced by "There's no such thing as a free ride."
D) lack of incentive for consumers to pay for a nonexcludable good.