Why is "unde imus" not accepted? The mouseover indicates ubi, unde, and quo as options for "where," but the difference has not yet become apparent for me.
I take it "quo" is "where to."
Yes, quo is "where to". Unde is "where from" so unde imus would be more "Where are we going from?".
And ubi is more "where" as in location without movement. "Where is Rome?" -> Ubi Roma est?.
What is the difference between "ubi" and "quo"?
quo -> 'to where?' - destination, direction
ubi -> 'where?' - location, no movement to or from