阅读理解。 There are two methods by which hydrogen (氢) can be used to power cars. The first way is to use hydrogen to drive the engine, in much the same way as many cars use gas. The second method is to use the reaction of hydrogen with oxygen in a battery, making the car a kind of electric one. The dream of producing hydrogen in the car while driving along by electrolyzing (电解)water is a long way off, so we are still at the period of batteries and filling the tank with hydrogen gas. This is the difficulty for potential car users and producers. There are only sixteen hydrogen filling stations in Los Angeles and none in 99% of other cities worldwide. Indeed, some of the big name automobile producers have pulled out of the race to put the first practical hydrogen car on the streets. Ford and GM have announced that they are pulling out in America and so has Renault in France. However, the Japanese companies are pressing on. In fact, Honda introduced its first hydrogen fuel cell car in 1999. They are now producing second generation hydrogen car known as the FCX Clarity. Guess where they are available for sale? In only one city because of its filling stations. Honda thinks that they could go into full-scale production of the FCX Clarity by 2020 if the world is prepared for them by then. Then there are hydrogen-powered buses in several European cities including Amsterdam, Barcelona, Hamburg, London, Luxembourg and Madrid. Lotus, the makers of London taxis, have announced that they propose to manufacture hydrogen-powered taxis in time for the London Olympics. So, the hydrogen vehicle is out there and the numbers will be growing fairly soon. The buses go back to their bus station, where an electrolyzing machine changes water into fuel for them to fill up on and the same will be the case for many of London's taxis. Unfortunately, getting fuel is not the only difficulty for the average motorist, a number of these vehicles cost about $300,000 each. 1.According to the text, hydrogen-powered buses _____. A. can easily be filled up with gas. B. are likely to sell well in the future. C. are mainly used in the United States D. won't be used in the London Olympics 2. What does the underlined word 'them' in paragraph 5 refer to?_____. A. Japanese companies B. Hydrogen buses C. The FCX Clarity D. Filling stations 3. Where are hydrogen cars currently available for sale?_____. A. In Barcelona B. In Hamburg C. In London D. In Los Angeles 4. We can learn from the text that ______. A. there are sixty hydrogen filling stations all over the world B. hydrogen vehicles fueled by water will be very expensive C. Honda will mass-produce the FCX Clarity by 2012 D. Honda produced its first hydrogen car in 1989