Since Telnet and SSH have nothing to do with leased lines those are out.
VTP is VLAN trunking Protocol and has nothing to do with leased lines, that is out.
VPN while will encrypt traffic is not something specific to leased lines.
Now DMVPN will create tunnels between multiple routers using GRE and with IPSec to encrypt traffic over those tunnels
Not telnet or VTP.
After that who knows, none are specific to leased lines so it comes down to what Cisco tell you it is which is often not what real life networks look like.
The question is not about whether a lease line can be encrypted with the below options.
The question is whether the provided options encrypt their own traffic when they travel through a lease line. And, you know what, if a service encrypts its traffic, it will encrypt it, irrespective of whether the medium is a lease line or a wireless link.
let's eliminate some answers:
For sure a telnet traffic is not encrypted. So we can eliminate this one.
Let's see VTP. You can set a password but this is authentication and it does not encrypt the packets. The VTP packets are still in clear text. In addition, this has no impact on encrypting a host traffic. So we eliminate this answer
VPNs: Some VPNs do encrypt traffic and some do not. It is not clear here what VPN type are we talking about and we cannot generalize to say that traffic is encrypted in VPNs ( because some VPNs really don't encrypt traffic). So we eliminate this answer.
DMVPN: This is also tricky. DMVPN like VPN can encrypt traffic but it is only optional. You can setup DMPVN and not use encryption. So we eliminate this answer
What remains is SSH. A SSH traffic is always encrypted, no matter what.
So whether you ssh a device across a lease line or across a wireless link, it is always encrypted.
The lease line words are quite confusing but when you see things from a helicopter point of view, these things makes more sense.
let me know if you need more clarification or if this is helpful
If the question was which of the following always encrypts data etc. I would agree with your logic.
But that isn’t the question so if you argue it might not be a VPN you could equally argue it could be a VPN.
It is just Cisco trying to catch people out instead of simply just testing people’s knowledge.
you are right that the wording on the question can be very misleading. I wish they would just ask the questions to test your knowledge and not try and trip you up.
It’s always been one of the reasons I avoided certifications to be honest.
Now I am having to do some for the company I am working for it is irritating me even more :)