They are on watch in front of the building. THIS IS BETTER
"on the watch" means something quute different. should be "on watch" or "guarding".
On the watch could have 2 meanings.
on the clock (which i think is what dkfour means), or
on the guard shift (as in on night watch) (which i think is what duo lingo means)
they are guarding in front of the building
For a language course, Duolingo is far too slow to make changes when app users let them know there is an issue with a sentence. Duo you should be more responsive. 'On watch' is the usual way of describing this action.
In a different example, Duolingo only accepts "keeping guard", while for this one, only "on the watch" is accepted. Very confusing. Standing guard is not even accepted.
Totally agree. This translation is ❤❤❤❤.
They are on guard in front of that building?
It accepts: They keep watch in front of the building.