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46. A ( for active sleep, in which dreaming appears)
47. C (And as the brain becomes more active, the eyes begin to move rapidly. This is sign of another change—the change is that a person is dreaming. )
48. A ( If a person continues to sleep, the brain temperature rises, the amount of blood in the brain increases, the body becomes very, very still, and the brain goes from being inactive to being active. And as the brain becomes more active, the eyes begin to move rapidly. This is sign of another change—the change is that a person is dreaming.)
49. C ( Scientists have found that everyone dreams for about one and a half hours a day, and that everyone dreams from three to seven times a night, though in ordinary life a person may remember none or only one of these dreams. )
50. C (and everyone needs to dream in order to keep healthy )