An administrator needs to manage a vRealize Operations cluster using the Admin UI.

 The two actions that are possible to manage a vRealize Operations cluster using the Admin UI are uploading and installing vRealize Operations PAK files, and enabling or disabling high availability for the vRealize Operations cluster. Uploading and installing vRealize Operations PAK files is an action that allows the administrator to update the vRealize Operations software, add new features, or install management packs1. Enabling or disabling high availability for the vRealize Operations cluster is an action that allows the administrator to configure the cluster to tolerate the failure of one or more nodes, and to ensure the continuity and availability of the vRealize Operations services2. Deploying a new vRealize Operations node OVA (option A) is not an action that can be performed using the Admin UI, as it requires the use of the vSphere Client or the vSphere Web Client to deploy the OVA file to the vCenter Server3. Activating a vRealize Operations native management pack (option C) is not an action that can be performed using the Admin UI, as it requires the use of the vRealize Operations Manager UI to access the Solutions page and activate the management pack4. Configuring a DNS server on the vRealize Operations nodes (option E) is not an action that can be performed using the Admin UI, as it requires the use of the command-line interface (CLI) to access the node settings and configure the DNS server5. References:

1: VMware vRealize Operations Specialist Exam 2023 (5V0-35.21) Exam Guide, VMware, 2021, p. 11.

2: VMware vRealize Operations Specialist Exam 2023 (5V0-35.21) Exam Guide, VMware, 2021, p. 12.

3: vRealize Operations Manager Installation and Configuration Guide, VMware, 2021, p. 17.

4: vRealize Operations Manager Installation and Configuration Guide, VMware, 2021, p. 31.

5: vRealize Operations Manager Installation and Configuration Guide, VMware, 2021, p. 25.