U.S. President Barack Obama on Wednesday paid honor to health care workers who have treated Ebola patients in West Africa, calling them “heroes”_________ to be applauded rather than discouraged.
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.
24. He apologized for his mistake, saying that he ___________no offence.