In which of the following circumstances would a cartel be most likely to work ?

In which of the following circumstances would a cartel be most likely to work ?

A. The market for copper, where there are very few producers and the product is standardized.
B. The fast-food market where there are a large number of producers but the demand for fast food is inelastic
C. The coffee market where the product is standardized and there are a large number of coffee growers.
D. The automobile industry, where there are few producers but there is great product differentiation.