题干

切除老鼠体内的甲状腺,10d后将其同没有切除甲状腺的老鼠相比,切除甲状腺的老鼠的代谢能力明显下降,并且无法检验出其血液中甲状腺激素。切除5d后,将溶解于某溶剂的一定量的甲状腺激素给老鼠连续注射5d,过10d后观察,其物质代谢能力没有下降。由此可推测:甲状腺激素能增强物质的代谢能力。为了证明这一推论,有必要进行对比实验,以作观察比较。你认为下列哪项为最适宜的对比实验组(   )

A:既没有切除甲状腺,又未注射甲状腺激素的实验组

B:从进行切除后的第1d开始,只注射用于该实验溶剂的实验组

C:从进行切除后的第5d开始,只注射用于该实验溶剂的实验组

D:将溶解于另一种溶剂的(与上述溶液不同)的甲状腺激素注射到刚刚做完切除手术的实验组

上一题 下一题 0.0难度 选择题 更新时间:2015-03-04 10:49:57

答案(点此获取答案解析)

C

同类题5

完形填空

    Imagine loving someone so much that you'd swim more than 5, 000 miles to see him or her. Dindim manages to swim that far every year to 1 his friend Joao. This is 2 not only because of the love between the two friends, but because Dindim is3a penguin. Joao found Dindim covered in oil, barely 4on a beach near his home. He picked him up, cleaned him off and brought him to his house where he 5 him and got him healthy again. Joao named him Dindim.

    After a week, he 6 the penguin back to the beach and tried to release him,7 Dindim refused to leave Joao. They 8 together for the next eleven months. Then, Dindim disappeared.9 Joao thought he'd never see his friend again. But just a few months 10 Dindim was back. He found Joao on the beach, and followed him home. Each year he 11four months to live with other penguins. For the other eight months, he lives with Joao. Joao says that each time they meet again, Dindim seems 12 to see him. He says he loves the penguin as if he were his own 13 He feels certain that Dindim loves him in the14way. Ecologist Carl Safina says that animals can and do love humans. He writes and speaks a lot about animals and their 15. According to Carl, it's obvious that animals feel love for humans. What's less obvious is whether or not humans love animals enough to 16 them. Hundreds of thousands of animals are 17 by the same oil that covered Dindim when Joao found him.

    Fifty percent of 18 has disappeared in the last 40 years because of humans'19 their habitats. Scientists say we're in a new mass extinction period. In the next two 20 they predict that we'll lose 75 percent of the remaining species on earth.