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Explanation:

<em><u>Bitcoin is a digital currency which operates free of any central control or the oversight of banks or governments. Instead it relies on peer-to-peer software and cryptography. A public ledger records all bitcoin transactions and copies are held on servers around the world</u></em>
Answer:
b. signed by both parties
Explanation:
The Uniform Commercial Codes includes the law of frauds. This is a state law which generally requires a certain contracts that is in writing and is signed by one of the parties to be enforceable.
It states that a sales agreement which is of $500 or more than that must be evidenced in a written form. The Uniform Commercial Codes confirmation memorandum of merchants allows that two parties or merchants having an oral agreement is bound to have a memo or a letter which is signed by only one party and which stands without objection for at least ten days.
Hence, confirmation memorandum signing by both the two parties is not requirement in UCC.
Thus the correct option is (b).