Which of the following is an example of a duopoly market?
a. boeing, airbus, and bombardier are the three aircraft manufacturing companies in the world.
b. debeers controls 70 percent of the market share in diamonds and the rest is shared by a few other companies.
c. the city of portland has three major cab service companies.
d. visa and mastercard exercise control over the electronic payment processing market in the world.

The correct answer is letter "D": Visa and MasterCard exercise control over the electronic payment processing market in the world.

Explanation:

A duopoly takes place when two companies dominate most part of a market. It is a type of oligopoly since small firms are under control of the market. Though, when the two companies collude on prices, the oligopoly has the same characteristic as a monopoly.

In that case, Visa and Mastercard are a duopoly since they control electronic payments on Europe and the U.S.

answerthe above statement is (true);

answer(d) encourage cooperation by improving the chances of mutually agreeable transactions;