Oooh.
@clearstream, I like that option C explanation. Would make for a neat system of inventory management too. Different items could have a different dc and the check could be based on different skills as well.
Do you have a climbing kit? Make an athletics dc X check. Do you have parchment? Maybe a knowledge check. So on and so forth. The more esoteric the equipment especially in context (umm, you are travelling over flat plains, why would you have a climbing kit?) modifies the dc.
Gonna steal that for my next campaign.