题目内容：
The Recycling Rate for Tires In Japan, the recycling rate for tires was already 93 percent in 1993, Discarded tires are recycled here in three ways. The most familiar involves simply using them "as is"--in their original shape for such things as playground equipment in schools and public parks. They are even used in some "bullet train" tracks as shock absorbers.Another popular use of discarded tires involves extracting rubber for processing into new products. "You can recycle rubber 100 percent, and as often as you wish. Rubber used in making tires is especially strong, so the rubber derived from scrapped(报废的)tires can be used in various ways," says Minoru Muraoka, president of Muraoka Rubber Co. who is bent on(致力于)recycling tires. In addition to being reused in tires, recycled rubber is used to make sheet rubber. Also, powdered rubber is used to make roof tries and slabs for sidewalks, thus contributing to improving the looks of our cities.
The third use for scrapped tires is as fuel. Half of all scrapped tires are currently used for this purpose at various installations requiring large amounts of heat energy.
Furthermore, Takeji Kobata, a researcher in Hokkaido has developed an epoch-making technology for making activated carbon (活性炭) by burning used tires. Activated carbon made from tires is of better quality and has greater absorptive power than other varieties already on the market. With the Kobata method, 1. 5 kilograms of activated carbon can be obtained from a single 7-kilogram automobile tire. Kobata has already obtained manufacturing patent (专利) in the United States, Canada and Taiwan, and has also opened the patented process to the public in Britain, Germany, France and BrazilThe passage is mainly about______ A．using tires in their initial shape
B．how to reuse discarded tires
C．how to recycle activated, carbon
D．the recycling rate of tires in Japan
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