39. People who cannot d______ between colors are said to be color-blind.

38. The man shamelessly a______ his wife and child for another woman.

37. Dust soon a______ if rooms are not swept.

36. A______ is an important branch of science.

35. Big businesses enjoy certain p______ that smaller ones do not.

34. Exercise will increase your a______ for food.

33. His first p______ was to make a thorough investigation.

32. Men in the post office c______ mail according to places it is to go.

31. The meeting discussed how to p______ the co-operation between the two countries.

28. The l______ of his argument persuaded us that he was right. 29. They soon overcame the language b______ after they went to England. 30. A good deal of adult education is accomplished by the mass m______. Unit 4