With the economic situation worsening _____, shopkeepers have to sell their goods _____ a big discount to attract customers.
He is a man of few words, and seldom speaks until _______ to.
Though I have often heard this song _______. I have never heard you _______ it.
Tony was very unhappy for _______ to the party.
Though ________ money, his parents managed to send him to university.
The research is so designed that once _______ nothing can be done to change it.