Bookstores Often Sponsor Author Book-Signing Events

Bookstores often sponsor author book-signing events.When a famous author came to Olivia's local bookstore,Olivia had to buy her book from the local store weeks before the signing and leave it at the store to be picked up at the time of the signing.The bookstore adopted this policy in order to

A) allow the author to sign many books in advance,speeding up the line.
B) maintain high levels of security at the signing.
C) prevent people from bringing in copies of the book that had been purchased elsewhere.
D) prevent people from plagiarizing the author's book.