gre阅读练习每日一篇(三十四)_GRE阅读

gre阅读练习每日一篇(三十四)

　　 That of a farmer whose crops have failed because the normal midseason rains did not materialize and no preparations for irrigation had been made

　　 That of a long-distance runner who loses a marathon race because of a wrong turn that cost him twenty seconds

　　 That of shipwrecked sailors at sea in a lifeboat, with one flask of drinking water to share among them

　　 That of a motorist who runs out of gas a mere five miles from the nearest gas station

　　 That of travelers who want to reach their destination as fast and as cheaply as possible, but find that cost increases as travel speed increases

　　25. According to the passage, the ultimate goal of the current research on nitrogen fixation is to develop

　　 strains of Rhizobium that can enter into symbioses with existing varieties of wheat, rice, and other nonlegumes

　　 strains of Rhizobium that produce more ammonia for leguminous host plants than do any of the strains presently known

　　 varieties of wheat, rice, and other nonlegumes that yield as much as do existing varieties, but require less nitrogen

　　 varieties of wheat, rice, and other nonlegumes that maintain an adequate symbiotic relationship with nitrogen-fixing bacteria and produce high yields

　　 high-yielding varieties of wheat, rice, and other nonlegumes that are genetically equipped to fix nitrogen from the air without the aid of bacteria