Luxury brands often use to dispose of special-run, sample, overstock, or liquidation goods.

The answer is Shopping communities
Shopping communities refers to a group of like-minded individuals that discuss and share informations regarding a certain niche of product.
Luxury brands like to give the most acknowledged member of such communities their product endorsement in order to increase their brand awareness.

Answer(d); /// in the absence of transaction costs,private parties can solve the problem of externalities on their own;