As nobody here knows what is wrong with the machine, we ________send for an engineer to handle the problem.
38. Mr. Black ______ home because his briefcase is still on the desk.
37. All animals, ______ their size, breathe once for every four heartbeats.
36. ______ has helped to save the drowning girl is worth praising.
35. ______ the house prices have risen sharply, the number of buyers is as great as ever.
34. Is this the reason ______ at the meeting for his carelessness in his work?