<閱讀測驗>第41至44題為題組 The prickly pear cactus is such a powerful symbol in Mexico that it occupies a prime spot on Mexico’s national flag. The plant was considered sacred by the ancient Aztecs， and modern-day Mexicans eat it， drink it， and even use it in medicines and shampoos. Now scientists have come up with a new use for the bright green plant: producing renewable energy. Known locally as nopal， the prickly pear is farmed on a massive scale in Mexico. Over the years， only the edible soft inner flesh has been used. The cactus’s thick outer layer (i.e.， husk)， with all those spines， had always been viewed as a waste product until researchers developed a biogas generator to turn the husks into electricity. The pilot project dedicated to developing the cactus biogas generator began in the south of Mexico City. The area produces 200，000 tons a year of prickly pear cactus—up to 10 tons of which ends up as waste on the floor of the cactus market each day. Then， a local green energy startup company got the idea to turn that waste into energy. The generator is now in place at the cactus market， where the vendors are enthusiastic about this new way to utilize the tons of cactus husks that once went directly into the trash. The prickly pear has a number of advantages over other biofuel crops， such as wheat， sugarcane， and soybeans. For one thing， only the husk of the cactus is used for generating biofuel， while its inner flesh is still preserved for food. Therefore， using the plant as a fuel source will not put pressure on food prices. Moreover， the cactus requires minimum water， and thus is not grown on traditional agricultural pasture. This means that no increased competition arises for the water or land presently used for food production. The project in Mexico City has brought new hope to reducing the use of fossil fuels. If it can be expanded， the prickly pear could be the key to Mexico’s energy future. 41. What is the purpose of this passage? (A) To argue for the benefits of nopales. (B) To introduce a new source of energy. (C) To predict the future agriculture policy of Mexico. (D) To change people’s ideas about energy consumption.
