Hello Jonk,
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
