职称英语考试理工类完形填空备考必备提高练习(9)

　　Spider webs are more than homes, and they are ingenious traps. And the worlds best web spinner may be the Goldern Orb Weaver spider. The female Orb Weaver spins a web of fibers thin enough to be invisible to insect prt, yet _____1____ enough to snare a flying bird without breaking.

　　The secret of the webs strength? A type of super-resilient ____2____ called dragline. When the female spider is ready to ____3_____ the webs spokes and frame, she uses her legs to draw the airy thread out through a hollow nozzle in her belly. Dragline is not sticky, so the spider can race back and forth along ____4___ to spin the webs trademark spiral.

　　Unlike some spiders that weave a new web every day, a Golden Orb Weaver _____5_____ her handiwork until it falls apart, sometimes not for two years1. The silky thread is five times stronger than steel by weight and absorbs the force of an impact three times better than Kevlar, a high-strength human-made ____6____ used in bullet-proof vests. And thanks to its high tensile strength, or the ability to resist breaking under the pulling force called tension, a single strand can stretch up to 40 percent longer than its original _____7____ and snap back as well as new. No human-made fiber even comes ____8____.

　　It is no ____9____ manufacturers are clamoring for spider silk. In the consumer pipeline: high-performance fabrics for athletes and stockings that never run2. Think parachute cords and suspension bridge cables. A steady _____10_____ of spider silk would be worth billions of dollarsbut how to produce it? Harvesting silk on spider farms does not ____11_____ because the territorial arthropods have a tendency to devour their neighbors.

　　Now, scientists at the biotechnology company Nexia are spinning artificial silk modeled after Goldern Orb dragline. The ____12____ step: extract silk-making genes from the spiders. Next, implant the genes into goat egg cells. The nanny goats that grow from the eggs secrete dragline silk proteins in their ______13____ . The young goats pass on the silk-making gene without____14____ help from us, says Nexia president Jeffrey Turner. Nexia is still perfecting the spinning process, but they hope artificial spider silk will soon be snagging customers ____15____ the real thing snags bugs.

　　1. A) tough B) soft C) large D) smooth

　　2. A) cloth B) silk C) nylon D) wool

　　3. A) repair B) pull C) move D) weave

　　4. A) him B) her C) it D) those

　　5. A) refixes B) reproduces C) remakes D) reuses

　　6. A) metal B) mass C) material D) model

　　7. A) bredth B) length C) height D) strength

　　8. A) close B) well C) open D) awake

　　9. A) hurry B) worry C) wonder D) use

　　10. A) shipment B) supply C) run D) exchange

　　11. A) run B) go C) deal D) work

　　12. A) previous B) foremost C) first D) front

　　13. A) milk B) meat C) lungs D) muscle

　　14. A) no B) any C) some D) many

　　15. A) as fast as B) as gently as C) as fully as D) as little as