Rosa Sends an Offer to Kellen That Requires Acceptance to Be

Rosa sends an offer to Kellen that requires acceptance to be made by U.S.mail.Kellen accepts in a timely manner,but sends the acceptance by FedEx which delivers the acceptance to Rosa two days faster than the U.S.mail would.Under traditional common law rules,has Kellen accepted Rosa's offer?

A) No,since the offer specified a particular manner of acceptance that was not used.
B) Yes,since FedEx was faster than the U.S.mail.
C) No,since the acceptance was delivered by a private,rather than a public,delivery service.
D) Yes,since acceptance sent in any form-even if early or delayed-confirms the offer.