The question is aimed at the standard three tiered network design.
Typically in this design you would run a routing protocol over layer 3 links between the Core and Distribution tiers.
Then you would trunk VLANs over Layer 2 links between the Distribution and Access tiers.
See below a couple of links for more details
Thanks for the reply, but I understand the campus network design concepts and that VLANs should terminate at the distribution layer as a best practice as per the local design (as opposed to end-to-end design).
But the answers provided are references to OSI model layer concepts. There is no such thing as a link that is purely Layer 3. You need some physical media to transmit data (layer 1) and you need some mutual protocols to define how the bits are to be interpreted and how they are transmitted (layer 2). Without these things layer 3 functionality isn't possible.
If anything this question is poorly worded. Had the question been: "What is the highest Layer of the OSI model that should be implemented in the links between the Core and Distribution layers?" (or something) then I would understand why you would only select Layer 3
NinjaEdit: Basically the issue for me here is that they imply that Layer 2 links are strictly VLAN while mac-addresses, CDP, LLDP, STP are not part of what it means to be a Layer 2 link and therefore should not be used in links between core and distribution switches.