-What has made him in such a low mood recently?-_____by his father for not passing the exam.
29. Tired of work through the year, she desired to _____ and make an independent life for herself.
28. The book was written _____ careful observations and detailed studies.
27. The development of science and technology must benefit people _____ harm them.
26. — Ring me at six tomorrow morning, will you? — Why that early?
25. Mike _______ have known the solutions to this problem, or he would have told us.