By saying that the book of "Grail Bird" could "easily be a book about the hunt for Bigfoot", the author means that _____.

A．the book is merely about the hunt for impossible things.
B．if the bird had not been discovered by the researchers, the book would have been like all the books about Bigfoot - only legends, no facts and truths.
C．the hunt for the ivory-billed woodpecker enjoys similarity to the hunt for Bigfoot, because both of them are rare animals.
D．the book is about the human obsession of finding legendary animals and about their guilty conscience facing nature.