Accidents are caused; they don't just happen. The reason may be easy to see: an overloaded

tray, a shelf out of reach, or a patch of ice on the road. But more often than not there is a chain of events leading up to the misfortune—frustration(挫折), tiredness, or just bad temper—that show what the accident really is, a sort of attack on oneself.

Road accidents, for example, happen frequently after a family quarrel, and we all know people who are accident-prone(有倾向的), so often at odds with(和...争执) themselves and the world that they seem to cause accidents for themselves and others.

By definition(定义), an accident is something you cannot predict(预测)to avoid, and the idea which used to current, that the majority(多数)of road accidents by a minority(少数) of criminally(犯罪地) careless drivers, is not supported by insurance statistics. These show that most accidents involve ordinary motorists in a moment of carelessness or thoughtlessness.

It is not always clear, either, the law requires all factories to take safety precautions(预防), and most companies have safety committees to make sure that the regulations are observed, but still, every day in Britain, some fifty thousand men and women are absent from work due to accident. These accidents are largely the result of human error or misjudgment—noise and fatigue(疲劳), boredom or worry are possible factors which contribute to(促使) this. Doctors who work in factories have found that those who drink too much, usually people who have a high anxiety level, run three times the normal risk of accidents at work.

According to the author, the accidents are mainly caused by ______.

A．external(外部的) conditions

B．people's internal(内部的) conditions influenced by physical or mental factors

C．slippery(滑的) rod&

D．a chain of events