Who should be creating the list of items, the page view-model or popup view-model?

I have a page view-model which shows a popup (using a user navigation service) asking user to select from a list of items. The popup has its own view-model. The list of items is created based on a criteria, and items belong to a Model. For example, a Teacher having to select from several Classes.

Who should be constructing the list of items? Should it be:

a. The page view-model and pass it to the popup view-model

b. The popup view-model?

c. Neither, creating the list of items belongs somewhere else (where?)

Which one is best and why?