题目

两种气态烃组成的混合气体完全燃烧后得到CO2和H2O的物质的量随混合烃的总物质的量的变化如图所示，则下列对混合烃的判断正确的是(     ) ①一定有乙烯；②一定有甲烷；③一定有丙烷；④一定无乙烷；⑤可能有乙烷；⑥可能有丙炔。 A．②③⑤    B．⑤⑥  C．①②       D．②④⑥ 答案：DWithin fifteen years Britain and other nations should be well on with the building of huge industrial complexes (结合)for the recycling of waste. The word "rubbish"  could lose its meaning because everything that goes into the dumps would be made into something useful. Even the most dangerous and un­pleasant wastes would provide energy if nothing else.The latest project is to take a city of around half a million inhabitants and discover exactly what raw materials go into it and what go out. The aim is to find out how much of these raw materials could be provided if a plant for recycling waste were built just outside the city. This plant would recycle not only metal such as steel, lead and copper, but also paper and rub­ber.Another new project is being set up to discover the best ways of sorting and separating the rubbish. When this project is complete, the rubbish will be processed like this: first, it will pass through sharp metal bars which will tear open the plastic bags in which rubbish is usually packed; then it will pass through a powerful fan to separate the lightest elements from the heavy solids; after that grounders and rollers break up everything that can be broken. Finally the rubbish will pass under magnets, which will remove the bits of iron and steel; the rubber and plastic will then be sorted out in the fi­nal stage.The first full-scale giant recycling plants are, perhaps, fifteen years away. Indeed, with the growing cost of transpor­ting rubbish to more distant dumps, some big cities will be forced to build their own recycling plants before long.1. The main purpose of the passage is ________.A. to show us a future way of recycling wastes  B. to tell the importance of recycling wastesC. to warn people the danger of some wastes    D. to introduce a new recycling plant2. How many stages are there in the recycling process?A. 3.                 B. 4.               C. 5.                          D. 6.3. What is the main reason for big cities to build their own re­cycling plants?A. To deal with wastes in a better way.  B. It’s a good way to gain profits.C. It’s more economical than to dump wastes in some dis­tant places.D. Energy can be got at a lower price. 4. The first full-scale huge recycling plants ________.A. have been in existence for 15 years   B. takes 15 years to buildC. can’t be built until 15 years later       D. will remain functioning for 15 years