Which of the Following Is a Necessary Prerequisite for Legally

Which of the following is a necessary prerequisite for legally claiming a reward?

A) A promise of completing the requested act is sufficient for a claimant to claim the reward.
B) Knowledge of the reward before completing the requested act is necessary to claim the reward.
C) The claimant can claim the reward even if he or she came to know of the reward subsequent to completing the act.
D) The offeror cannot withdraw the reward once the offer has been placed in the public domain.