A、Raising safety standards for vehicles. B、Establishing speed limits on more roads. C、Limiting the number of vehicles on express

The motor vehicle has killed and disabled more people in its history than any bomb or weapon ever invented. Much of the blood on the street flows essentially from uncivil behavior of drivers who refuse to respect the legal and moral rights of others. So the slaughter 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 principle 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 these killers go even beyond carelessness to total negligence.
    Researchers have estimated that as many as[17]80 percent of all automobile accidents can be tributed to the psychological condition of the driver. Emotional upsets can distort driver’s reactions, slow their judgment, and blind them to dangers that might otherwise be evident. The experts warn that it is vital for every driver to make a conscious effort to keep one’s emotions under control.
    Significant legal advances have been made towards safer driving in the past few years. Safety standards for vehicle have been raised both at the point of manufacture and through periodic road-worthiness inspections. In addition, speed limits have been lowered. Due to these measures, the accident rate has decreased. But the accident experts still worry because there has been little or no improvement in the way drivers behave. The only real and lasting solution, say the experts, is to convince people that driving is a skilled task requiring constant care and concentration. Those who fail to do all these things present a threat to those with whom they share the road.
16. Why are traffic accidents regarded as a social problem?
17. Why does the passage mention the psychological condition of the drivers?
18. What legal measures have been taken towards safer driving in the past few years?
19. What is the main purpose of the passage?