A customer wants to provide wireless access to contractors using a guest portal on Cisco ISE. The portal is also used by employees. A solution is implemented, but contractors receive a certificate error when they attempt to access the portal. Employees can access the portal without any errors. Which change must be implemented to allow the contractors and employees to access the portal?

A. Install an Internal CA signed certificate on the Cisco ISE.
B. Install a trusted third-party certificate on the Cisco ISE.
C. Install an internal CA signed certificate on the contractor devices.
D. Install a trusted third-party certificate on the contractor devices.