Which of the Following Is an Example of a Market

Which of the following is an example of a market failure?

A) There are not enough tickets available to concerts of extremely popular performers and artists
B) The price of medical care has risen dramatically as a result of the introduction of sophisticated equipment and procedures
C) Successful public schools provide benefits to the students who attend them, as well as to the community as a whole including those who don't go to those public schools
D) Extensive decreases in the prices of electronic equipment resulted in large numbers of bankruptcies in the computer industry