Sally is promoting her online store that sells vintage goods and custom artwork. what does she need to include for unique product identifiers?

Q) Sally is promoting her online store that sells vintage goods and custom artwork. what does she need to include for unique product identifiers?

Ans: 
Submit '1' as the 'mpn' attribute
Put 'false' in the 'identifier exists' attribute
Put 'unavailable' in the 'gtin' attribute
Submit a randomly generated number in the 'gtin' attribute