The factory was built in a secret place, around ______ high mountains.
I can’t find my watch. I must have______it in the hotel.
Is Mr. Wang good at drawing his students into___discussion?
______side of the street is lied with different shops, _______ of which sell electronic products.
He arrived here at noon, ______in the day, and he went out and came back_______ in the day.
Only when _____ possible to settle the problem.