The Key Message from the Authors' Discussion of Crop Circles

The key message from the authors' discussion of crop circles is that

A) aliens or some form of extraterrestrial being have been trying to communicate with humans for hundreds of years.
B) the causes of some real-world events are unexplainable and unknowable.
C) scientific thinkers must select the simpler of two claims that fit with the available evidence.
D) hoaxers often impede scientific progress into the understanding of unexplainable events like the English crop circles.