問題詳情

California condors are North America’s largest birds, with wind-length of up to 3 meters.In the 1980s, electrical lines an d lead poisoning nearly drove them to dying out. Now, electricshock training and medical treatment are helping to rescue these big birds.In the late 1980s, the last few condors were taken from the wild, and there are now more than150 flying over California and nearby Arizona, Utah and Baja in Mexico.Electrical lines have been killing them off. “As they go in to rest for the night, they just don’tsee the power lines,” says Bruce Rideout of San Diego Zoo. Their wings can bridge the gapbetween lines, resulting in electrocution if they touch two lines at once.So scientists have come up with a shocking idea. Tall poles, placed in large training areas,teach the birds to stay clear of electrical lines by giving them a painful but undeadly electricshock. Before the training was introduced, 66% of set-freed condors died of electrocution.This has now dropped to 18%.Lead poisonous has proved more difficult to deal with. When condors eat dead bodies ofother animals containing lead, they absorb large quantities of lead. This affects their nervoussystems and ability to produce baby birds, and can lead to kidney failures and death. Socondors with high levels of lead are sent to Los Angeles Zoo, where they are treated withcalcium EDTA, a chemical that removes lead from the blood over several days. This work isstarting to pay off. The annual death rate for adult condors has dropped from 38% in 2000 to5.4% in 2011.Rideout’s team thinks that the California condors’ average survival time in the wild isnow just under eight years. “Although these measures are not effective forever, they are vitalfor now,” he says. “They are truly good birds that are worth every effort we put into recoveringthem. ”
60.California condors attract researchers’ interest because they _________.
(A) are active at night
(B) had to be bred in the wild
(C) are found on in California
(D) almost died out in the 1980s

參考答案

答案：D
難度：適中0.5
統計：A(0),B(0),C(0),D(0),E(0)

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