How Are "Gold Farms," Such as Those Set Up to Play

How are "gold farms," such as those set up to play World of Warcraft, different from traditional sweatshops?

A) They usually meet minimum working standards for health and safety.
B) They purchase and consume virtual goods instead of material goods.
C) They may not pay much better wages, but the work is much more entertaining.
D) They exploit workers to produce virtual goods instead of material goods.