题干

检验某可燃烧的化合物是否含有氢、碳、氧3种元素,在该物质完全燃烧后还必须进行的实验是:①用带火星的木条检验;②用无水硫酸铜检验;③用澄清石灰水检验;④对反应物、生成物进行称量.以下选项中正确的是(  )


A:①②③④  

B:②③④

C:①②③

D:②③

上一题 下一题 0.0难度 选择题 更新时间:2019-01-11 12:33:13

答案(点此获取答案解析)

B

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阅读理解

    Animal training refers to teaching animals specific responses to specific conditions or stimuli (刺激). Training may be for the purpose of companionship, detection, protection, entertainment or all of the above.

    An animal trainer may use various forms of reinforcement (强化) or punishment to condition an animal's responses. There are many ways to train animals and as a general rule no legal requirements or certifications (证书) are required.

Chickens

    Training chickens has become a way for trainers of other animals (primarily dogs) to perfect their training technique.  Bob Bailey, former director of Animal Behavior Enterprises and the IQ Zoo, teaches in chicken training courses where trainers teach chickens to tell different shapes, to navigate an obstacle course and to chain behaviors together.

Fish

    Fish can also be trained. For example, a goldfish may swim toward its owner and follow him as he walks through the room, but will not follow anyone else. The fish may swim up and down, signaling the owner to turn on its aquarium (鱼缸) light when it is off, and it will skim the surface until its owner feeds it. Pet goldfish have also been taught to perform more complicated tasks, such as doing the limbo (a kind of dance) and pushing a miniature soccer ball into a net.

Pigs

    Among all animals, they are the third cleverest — monkeys, dolphins and pigs. Scientists think the training of pigs is easier than the training of dogs and cats. Pigs have a very good sense of smell. They can find things nearby or faraway. They can also help the police to find out drugs at an airport or at a train station.