A
The prickly pear cactus (仙人掌) is such a powerful symbol in Mexico that it occupies a prime spot on Mexico’s national flag. The plant was considered sacred(神圣的) 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(可食用的) soft inner flesh has been used. The cactus’s thick outer layer (i.e., husk), with all those spines(刺), had always been viewed as a waste product until researchers developed a biogas generator to turn the husks into electricity.
The pilot project(试点项目) devoted to developing the cactus biogas generator began in the south of Mexico City. The area produces 200000 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(商贩们) are enthusiastic about this new way to make use of 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(甘蔗), and soybeans(大豆). 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 lands. 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.
21. What is the main purpose of this text?
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.
22. What can you learn from the text?
A. Its soft inner part is often discarded.
B. It was not discovered until the modern era.
C. It turns into 200,000 tons of waste in Mexico each year.
D. It appears in an eye-catching place on Mexico’s national flag.
23. What advantage does the prickly pear cactus have over other biofuel crops?
A. It generates more energy. B. It will not influence food prices.
C. It may replace feed for livestock. D. It can increase global food production.
【答案】21. B 22. D 23. B
【解析】
【分析】本文是一篇说明文。文章介绍了仙人掌在墨西哥在生产可再生能源方面的价值。
【21题详解】
推理判断题。根据第一段“Now scientists have come up with a new use for the bright green plant: producing renewable energy.（现在，科学家们想出了这种绿色植物的一种新用途：生产可再生能源。）”及全文可推断，这篇文章的主要目的是引进一种新的能源。故选B。
【22题详解】
细节理解题。根据第一段“The prickly pear cactus (仙人掌) is such a powerful symbol in Mexico that it occupies a prime spot on Mexico’s national flag.（仙人掌是墨西哥的象征，它占据了墨西哥国旗的主要位置。）”可知，仙人掌它出现在墨西哥国旗上一个引人注目的地方。故选D。
【23题详解】
细节理解题。根据倒数第三段“Therefore, using the plant as a fuel source will not put pressure on food prices.（因此，使用这种植物作为燃料来源不会对食品价格造成压力。）”可知，仙人掌比其他生物燃料作物的优势是它不会影响食品价格。故选B。
