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A is corrent. The requirment is to determine under the UCC which of the instruments listed meets the negotiability requirement of being payable on demand or at a definite time. A is corrent because a promissory note is payable at a definite time if it is payable on a certain date, even when the holder may extend the time of payment.
B is incorrect because although the promissory note is payable one month after its date, the promissory note contains no date.
C is incorrect because the promissory note is not payable at a definite time when the maker has an option to extend the time of payment unless the extension is limited to a definite amount of time.
D is incorrect because the time is not definite when the promissory note is payable based on an event that is not certain as to its time of occurrence.