An Engineer Has Integrated a New DMVPN to Link Remote

An engineer has integrated a new DMVPN to link remote offices across the internet using Cisco IOS routers. When connecting to remote sites, pings and voice data appear to flow properly, and all tunnel stats show that they are up. However, when trying to connect to a remote server using RDP, the connection fails. Which action resolves this issue?

A) Adjust the MTU size within the routers.
B) Add RDP port to the extended ACL.
C) Replace certificate on the RDP server.
D) Change DMVPN timeout values.