Which of the Following Is an Example of the Free-Rider

Which of the following is an example of the free-rider problem?

A) John attends a lecture on investing in high-tech companies for which he paid $100 to hear.
B) Tom watches Mystery on his local PBS television station, but Tom does not contribute anything to PBS.
C) Sarah works overtime while her co-workers opt for a traditional schedule.
D) Jethro buys a skunk-hunting permit that he refuses to share with his sister.
E) Katie catches a swordfish in the ocean.