Choice "A" is correct. A firm offer (an offer that must remain open despite the absence of consideration) can be made only by merchants and must be in a signed writing.
Choice "b" is incorrect. If a firm offer does not state its period of irrevocability, it will remain open for a reasonable time not to exceed three months.
Choice "c" is incorrect. A firm offer is an offer that must remain open despite the lack of consideration.
Choice "d" is incorrect. The offeree need not be a merchant in a firm offer situation; only the offeror need be a merchant.
