If No Means of Communicating an Acceptance Is Specified in an Offer

If no means of communicating an acceptance is specified in an offer, which of the following is generally true?

A) The acceptance must be in writing.
B) The acceptance must be made verbally either by telephone or in person.
C) No valid contract may be entered into because the offer must specify a means by which to accept.
D) Acceptance may be made by any reasonable means.
E) Acceptance must be made orally or in writing within twenty-four hours.