The correct answer is TXT or CNAME record.

Domain ownership verification most commonly uses a TXT record because providers issue a verification token that you paste into a TXT record for the domain. Some providers accept or require a CNAME record as an alternative method that points a verification subdomain to a vendor controlled hostname so the provider can confirm control of the domain.

The option MX record is incorrect because MX record entries direct mail delivery to mail servers and they are not generally used for ownership verification.

The option Cloud DNS is incorrect because Cloud DNS is a managed DNS service and not a specific DNS record to add for verification. The question asks which record to add and not which service will host the record.

The option A record is incorrect because A record maps a hostname to an IPv4 address and it does not carry verification tokens or point to vendor verification hostnames in the way that TXT or CNAME records do.

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