[单项选择]The motor vehicle has killed and disabled more people in its brief history than any bomb or weapon ever invented. Much of the blood on the street flows (47)______ from uncivil behavior of drivers who refuse to respect the legal and moral rights of others. So the massacre (大屠杀) on the road may be regarded as a social problem. In fact, the enemies of society on wheels are rather harmless people, just ordinary people acting carelessly, you might say. But it is a (48)______ both of law and common morality that carelessness is no excuse when one’’s actions could bring death or damage to others. A minority of the killers go even beyond carelessness to total (49)______. Researchers have estimated that as many as 80 per cent of all automobile accidents can be attributed to the psychological condition of the driver. Emotional upsets can distort drivers’’ reactions, slow their judgment, and blind them to dangers that might (50)______ be evident. The experts warn that it is vital for ev