______ economy in some European countries worsening, many more workers had to be laid off.
27. She locked her room _____ a thief would break into it.
26. She said she would spend her holiday ___ Beijing.
25. Whenever I go to Beijing, ____ is quite frequent, I will go to visit the Great Wall.
22. The two boys fought and fought until one ______.
He will _____ our class to sing at the school singing contest.