Several upper-layer management and file transfer protocols use SSH as their secure transport foundation. SFTP is the SSH File Transfer Protocol and operates over SSH, making option C correct. STelnet is secure Telnet implemented over SSH, so option D is also correct. NETCONF commonly uses SSH as its transport protocol for secure configuration management and device orchestration, making option B correct as well.

Option A, DNS, does not use SSH as its normal transport protocol. Traditional DNS operates over UDP or TCP port 53, depending on the query or transfer type. Although DNS security extensions and encrypted DNS variants exist, they are not based on SSH. HCIA-Datacom emphasizes the role of SSH in secure network management because it replaces insecure plaintext protocols and provides confidentiality, integrity, and authentication. In practical Huawei enterprise deployments, SSH-based protocols are widely used for interactive device login, automated configuration delivery, and secure file operations. This question tests recognition of management protocols that inherit SSH's secure channel rather than protocols that operate independently at the application layer.