阅读理解。 What do people do with their old, out of date but still useful computers?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 away as the rubbish. Finally, some companies are thinking of ways to bring down the number of old computers. Sony has agreed to help recycle old Sony products (产品). Dell, Hewlett Packard and other companies now also take back some old computers. In some countries, laws have been passed, too. Computer companies have to pay for collecting and recycling their used products. And 70% of computer waste must be recycled. The idea behind the laws is that computer companies themselves should pay for 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 (慈善团体) 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 waste, too. 1. What do many people do with old computers? [     ] A. They repair them. B. They sell them. C. They send them to others. D. They stop using them. 2. How many computer companies are mentioned in the second paragraph? [     ] A. One. B. Two. C. Three. D. Four. 3. According to the laws in some countries, computer companies must . [     ] A. recycle most of their products B. collect all their used products C. repair and upgrade old computers D. make more cheaper computers 4. What do the organizations do to solve the problem of old computers? [     ] A. Help the computer companies to collect them. B. Repair and send them to those who need them. C. Help people to learn to use them. D. Turn rubbish into useful things. 5. What is the main idea of this passage? [     ] A. Repairing old computers. B. Encouraging to make cheap computers. C. Recycling old computers. D. Helping those who need computers.