Two goods are said to be complements if they are generally or necessarily consumed together, such as tea and sugar cubes or printers and ink cartridges. As some of you might remember, Nokia cellular phones were once very popular in Turkey. Almost everybody had one back then, but currently only few people have a Nokia. The company went bankrupt. However, no one would be interested in buying a Nokia even if it survived. Apple and Samsung have become the popular suppliers of cell phones today. This is an example for the shift in tastes and preferences of the customers. The correct answer is Choice D.