A notarial certificate must include the notary's signature and commission expiration date.

• A. Notary's signature and commission expiration date
• B. Notary's street address
• C. Document's file number
• D. Notary's date of birth

Answer: (A)

Notarial certificates must include the notary's signature and the commission expiration date to prove both who performed the notarization and that they were authorized to do so at the time. The signature serves as the official attestation that the act occurred and was witnessed by the notary, while the commission expiration date shows the notary was actively commissioned when the act took place. This combination ensures the notarization is valid and enforceable. Elements like the street address, document file number, or the notary's date of birth are not required to validate the act or establish authority, so they don’t belong in the certificate.