Which of these is true regarding tunnel configuration when deploying a Cisco ISR as a DMVPN hub router?

Which of these is true regarding tunnel configuration when deploying a Cisco ISR as a DMVPN
hub router?

A.
Only one tunnel can be created per tunnel source interface.

B.
Only one tunnel can be created and should be associated with a loopback interface for dynamic
redundancy

C.
The GRE tunnel key is used to encrypt the traffic going through the tunnel through the hub.

D.
You can run multiple parallel DMVPNs on the hub router, but each tunnel requires a unique
tunnel key.

Explanation:
Task 4 creates the mGRE tunnel interface. Enter the interface tunnel command and then configure
basic GRE parameters. The tunnel mode gre multipoint command designates the tunnel interface

as mGRE and the tunnel source command specifies the physical interface to which the GRE
tunnel is bound. The tunnel key command is required and must match the tunnel key configured
on the spokes. This command allows network administrators to run more than one DMVPN at a
time on the same router. The GRE tunnel key therefore uniquely identifies the DMVPN.