The correct answer is D. In FortiManager HA manual mode, the study guide explains what happens when members change: if the primary fails, you must manually promote a secondary and repoint the others, but that is not this scenario. For a failed secondary, the relevant exact extract is: ''if you remove a secondary member from the HA configuration, the primary FortiManager removes the secondary serial number from the central management configuration of FortiGate, and updates the managed FortiGate devices immediately.''

Operationally, in the HA configuration, removing that failed secondary means deleting its HA peer entry from the primary, which corresponds to removing the failed device's peer IP. A is false because manual HA is not transparent in this case. B is only a diagnostic detail. C applies when the primary fails, not a secondary.

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