Explanation: The correct answer is option C, conversion of the existing Instant APs to campus APs (CAPs). This is because the existing Instant APs can be converted to CAPs by changing their operating mode and pointing them to the MC. This way, the customer can leverage the existing APs and avoid purchasing new ones. The MC can then provide centralized management, configuration, and control for the APs.
Option A is incorrect because the purchase of Universal APs is not necessary. Universal APs are APs that can operate in either Instant or CAP mode without requiring a conversion. However, the existing APs can be converted to CAPs without buying new ones.
Option B is incorrect because Aruba ClearPass is not required to onboard the APs as CAPs in the new MC-based deployment. Aruba ClearPass is a network access control (NAC) solution that provides authentication, authorization, and accounting (AAA) services for wired and wireless devices. It is not involved in the conversion of Instant APs to CAPs.
Option D is incorrect because a Virtual Mobility Controller (VMC) is not a valid option to control Instant APs. A VMC is a software-based MC that runs on a hypervisor. It can control CAPs, but not Instant APs. Instant APs can only be controlled by another Instant AP acting as a Virtual Controller (VC).
References: The information can be referenced from the official HPE documents and learning materials available on HPE Press and Aruba Networks. Specifically, it aligns with the objectives outlined in Chapter 6: Wireless Network Design, where the Instant and CAP modes and the MC options are discussed. Designing Aruba Solutions Official Certification Study Guide Aruba Instant User Guide Aruba Mobility Controller Data Sheet