Add a TXT record to the domain DNS records is correct.

A DNS TXT verification proves control of the domain at the DNS provider so the vendor can confirm ownership without needing access to the web server. To verify a domain you add a specific verification string as a DNS TXT record and the vendor checks that the record resolves, which is the standard and automated method for domain-level verification.

Upload a verification HTML file to the site root is incorrect because that method requires control of the web hosting and HTTP access to the site. Some services accept an HTML file for site verification but it does not prove control of the domain at the DNS level and it is not the expected method for domain DNS verification in this scenario.

Send a message from an address at the domain to the vendor support team is incorrect because an email alone can be spoofed or misrouted and it relies on manual action by support staff. Vendors use automated DNS checks to provide a reliable cryptographic proof of control rather than manual email confirmation.

Arrange a live video session with support to present identity documents is incorrect because that process verifies a person not the domain. It is not a standard automated way to assert domain ownership and it would be impractical for routine domain verification for a service like CloudWork.

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