Which of the following is an example of an extended definition?

A. While there will probably never be a time when we do not have fish, there could come a time when we no longer have enough fish. The cause of this fish shortage is overfishing.
B. Overfishing occurs "when more fish are caught than the population can replace through natural reproduction," according to the World Wildlife Foundation. Once this occurs, a species is no longer "sustainable." Eighty-seven percent of all the world's fish stocks that we know about are at the "breaking point," according to the Environmental Defense Fund (EDF).
C. Overfishing, or fishing so much that there are not enough fish left, is a serious threat to the world's food supply.
D. The Merriam-Webster Learners Dictionary defines overfishing (noun) as "the act of catching too many fish so that there are not enough remaining."