问题 选择题

青霉素刚制造出来时,能杀死多种致病的细菌,疗效很好,但由于人们使用青霉素过多,使得有些细菌不再受青霉素的影响.细菌对青霉素抗药性增强的主要原因是(  )

A.青霉素的质量下降

B.细菌对青霉素选择的结果

C.青霉素的使用使细菌产生了抗药性变异

D.青霉素对细菌的抗药性变异进行选择的结果

答案

在青霉素刚被使用的时候,能够杀死大多数类型的细菌.但少数细菌由于变异而具有抵抗青霉素的特性,不能被青霉素杀死而生存下来,并将这些特性遗传给下一代.因此,下一代就有更多的具有抗药性的个体,经过青霉素的长期选择,使得有的细菌已不再受其的影响了.可见,细菌抗药性的产生是青霉素对细菌的变异进行选择的结果.

故选:D

完形填空

阅读下面的短文,并完成短文后的任务。

Draw a giraffe in your mind. How did you draw your giraffe? Does it have a long neck? Does it have long legs? Is it really tall? When people think of giraffes, they think of their long necks. A long neck and four long legs make the giraffe the tallest land animal on earth. A giraffe is 1.8m tall when it is born, and some giraffes get up to 6m tall when they are all grown up.

But did you know that giraffes also have long tongues? Have you seen the tongue of a giraffe before? A giraffe has a very long tongue which can hold and wrap (包) around objects. The tongue is designed for feeding, but it can be used in many different ways. For example, a giraffe can close its nose with its long tongue completely to keep out sand and dust. Also, a giraffe’s tongue is long enough to clean its owner’s ears as well!

The tongue is black in colour to protect it from getting sunburnt (晒伤). It is nearly 56cm long. Giraffe only eat plants, and a full grown giraffe can eat 33kg of leaves a day. When giraffes look for some tall trees to eat, they sometimes fight with elephants for food. Giraffes use their tongue to eat leaves from some tall trees. The giraffe’s tongue is a helpful tool for reaching leaves and breaking off branches.

任务一:根据短文内容回答下列问题。(注意:每题答案不超过10个单词)

小题1: What is this article mainly about?

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小题2:What does a giraffe feed on?

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小题3: What color is the tongue of a giraffe? Why?

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小题4: Give two examples of the use of the giraffe’s tongue.

(1) ___________________________________ (2) __________________________________

小题5:任务二:将文中划线的句子翻译成汉语。

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选择题