The three protocols found in the management plane from the options provided are:
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SSH (Secure Shell) - Used for secure remote administration and management of network devices.
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SNMP (Simple Network Management Protocol) - Used for collecting and organizing information about managed devices on IP networks and for modifying that information to change device behavior.
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Telnet - A protocol used for remote management of network devices, although it is less secure compared to SSH.
CDP (Cisco Discovery Protocol) is more of a discovery protocol rather than a management protocol.
So, the correct choice of three protocols from the management plane would be: SSH, SNMP, and Telnet.