This is a Weaken EXCEPT question, which means that the wrong answers will weaken the argument, while the right answer will either strengthen it or be irrelevant.

The conclusion drawn by the proponents of BASE jumping is that BASE jumping should be legalized. As evidence, they cite that people in a free society should be able to do as they please as long as they do not harm others in the process.

The central assumption in this argument is that BASE jumpers do not harm others while pursuing their sport. It's impossible to predict the right answer in an EXCEPT question; however, you can predict that the wrong answers will weaken the assumption by showing ways that BASE jumpers do harm others.

(A) is correct because it merely provides evidence that BASE jumpers don't injure themselves; this doesn't give any reason to think that BASE jumping shouldn't be legalized.

(B) and (E), if true, would show that the owners of buildings used in BASE jumping are harmed because of increased insurance or damage to the building.

(C) shows that municipalities or taxpayers are harmed because of the need for additional police units.

Finally, (D) means that some innocent bystanders are harmed by the BASE jumpers.