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Scientists have found that as cats became pets over the last 10,000 years, their brains have become smaller. This shows that a theory called “the domestication syndrome (驯化综合征)” is true.

This theory shows that when animals are tamed, their brains make fewer special cells (细胞) called neural crest cells (NCC). These cells have something to do with fear and excitement. Having fewer of these cells might make the brain smaller and change how animals look to and do with stress.

The scientists compared the skull (头骨) sizes of house cats and several types of wild cats from Africa and Europe. They found that house cats, and mixes of wild and house cats, have smaller skulls (and brains) than wild cats (including European wildcats and African wildcats). They also found that mixed-breed cats have brain sizes in between those of house cats and wildcats.

The main reason for this brain size reduction is that house cats live easier lives in more comfortable environments with fewer dangers and predators.

Other studies have shown that the brains of other tamed animals, like dogs and rabbits, have also become smaller compared to their wild relatives. Even human brains have become smaller over the past 28,000 years. Experts think that the change from being hunter-gatherers (狩猎采集者), ▲ , to being farmers with more peaceful lives may be the main reason for this brain size reduction.

1.What does the underlined word “tamed” mean in Chinese?

A 驯化.

B 野生.

C 捕捉.

D 引进.

解析：选A。A词义猜测题。根据第一段的“as cats became pets”和“the domestication syndrome (驯化综合征)”可知，随着猫变成宠物，它们的大脑变得更小，这证实了“驯化综合征”的正确性。由此可知，此处的tamed指的是“驯化”。故选A。

2.Which of the following cats has the smallest brain?

A European wildcats.

B House cats.

C African wildcats.

D Mixes of wild and house cats.

解析：选B。B推理判断题。根据第三段可知，家猫和混血猫的头骨比野猫小，混血猫的头骨介于家猫和野猫之间，即家猫的头骨最小。故选B。

3.What caused the smaller brains of cats?

A Technology development.

B Growing number.

C Comfortable environments.

D Health states.

解析：选C。C细节理解题。根据倒数第二段的“house cats live easier lives in more comfortable environments”可知主要是居住环境的变化导致了猫的大脑变小。故选C。

4.Which of the following can be put in the “ ▲ ”?

A who kept more animals

B who faced many dangers

C who had fewer relatives

D who lived more comfortably

解析：选B。B推理判断题。结合前文讲到，被驯化的家猫因为生活环境变得更舒适而导致大脑变小，本段列举了更多关于驯化综合征的例子，如狗和兔子，甚至人类也因为从狩猎采集者转变成生活更稳定安宁的农民，题空处应该与稳定安宁形成对比，狩猎采集者面临更多危险。故选B。

5.In which part of a magazine can we most probably read the passage?

A Science.

B Technology.

C Culture.

D History.

解析：选A。A推理判断题。根据全文内容可知，文章讲述了科学家对猫的大脑进行了相关研究，发现猫的大脑变小。属于科学研究。故选A。