Final answer:
Option C, penguins to explorers in Antarctica, best represents the relationship of birds on Skellig Michael to the monks there as both represent a natural element of interest to human observers.
Step-by-step explanation:
The relationship most like that of the birds on Skellig Michael to the monks there is option C, penguins to explorers in Antarctica. This analogy suggests a situation where the presence of one group (the birds or penguins) is of interest to the other group (the monks or explorers) due to the unique ecological or research opportunities they provide. Penguins are a natural part of the Antarctic ecosystem and are of significant interest to explorers and researchers, much like how the birds on Skellig Michael might have held significance for the monks, possibly for their natural beauty, as a food source, or even spiritual significance.