What do people do with their old, out-of-date but still useful computers? Most people don't know what to do with them. Many old computers are put away in homes. Many more are simply thrown out with the rubbish.
Some companies are thinking of ways to bring down the number of old computers. Sony has agreed to help recycle old Sony products. Dell, Hewlett-Packard and other companies now also take back some old computers.
In some countries, laws are being passed, too. Computer companies will have to collect and recycle their used products. And 70% of computer waste must be recycled. The idea behind the laws is that computer companies themselves should pay the cost. That will encourage them to make computers that are easier and cheaper to repair and upgrade（升级）.
Yet while many people are throwing away good computers, others cannot afford them at all. Hundreds of organizations are working to solve this problem. They collect and repair old computers. Some also teach others how to repair computers.
The computers then go to schools, charities and people who need them. Giving a used computer to one of these organizations can turn one person's rubbish into someone else’s useful things—and cut down on waste, too.
个容量为120的样本，则应抽取一年级的学生
