19．We all know that eating junk food can make us fat．However，a new study suggests that it can do more than that-it can also make us lazy，reported CBS News．
In the study，researchers at the University of California，Los Angeles，US divided 32female rats into two groups．The first group was fed a diet of healthy food such as corn and fish，while the second was given a diet of highly processed （加工的） food rich in sugar，namely"junk food"．
Within three months，the rats in the second group were already much fatter than those on the healthy diet．And when researchers trained the rats to do simple tasks，they found even more differences between the two groups rather than weight．
During the task-pushing a lever （杠杆） to receive a reward of sugar water-the rats on the junk food diet were found to be less willing to move，and they took longer breaks between each push than the lean rats did．
"It is as if the rat is thinking‘This is too much work'，"Aaron Blaisdell，leader of the study，told the Los Angeles Times．
But what about the possibility that the fat rats were less passionate about getting sugar water because they were already eating lots of sugar in their daily diet？That's why researchers repeated the tests by rewarding fat rats with plain water when they were extremely thirsty．However，the results came out just the same．
According to researchers，these differences suggest that junk food changed the chemistry in the rats'brains．
The experiment didn't end there．After six months，the rats'diets were switched，and the overweight rats were given a healthy diet for nine days．However，this change didn't help reduce their weight or improve their ability to perform tasks，which means the effects of their junk food diet persisted （持续存在）．"There's no quick fix，"said Blaisdell．
For a long time，we've believed that people become fat because they are lazy．But this study has proven the opposite to be true as well，which indicates that laziness and obesity are a"vicious cycle （恶性循环）"．
So，if you constantly feel tired，lacking any urge to get up from your chair，it could be that you've been studying too hard．But you should also pay attention to your diet．
46．During the first three months of the experiment by researchers at the University of California，C．
A．rats from the healthy diet group ate nothing but corn and fish
B．rats on the junk food diet ate more than those on healthy diet
C．rats on the healthy food diet performed better at simple tasks than those on the junk food diet
D．rats on the junk food diet seemed uninterested in sugary food
47．The researchers rewarded thirsty rats with plain water in the lever test toB．
A．help them control their weight
B．test whether fat rats lost interest in the test because they had taken enough sugar
C．change the diet habits of fat rats
D．find out the influence of sugar on rats'brains
48．The underlined word"there"refers toD．
A．after the rats on the junk food diet had worked hard to get sugar water
B．after the type of food rats prefer had been identified
C．after a quick cure for obesity had been found
D．after the fact that fatter rats are lazier than lean rats had been found
49．We can conclude from the article thatC．
A．fat people are usually lazier than lean people
B．people should switch between different types of diets to keep healthy
C．being overweight and being lazy can feed into each other
D．laziness is the main cause of weight problems
50．Which of the following is Not Right according to the passage？B
A．Eating junk food can make us fat．
B．Researchers got different results after repeated the tests to fat rats．
C．For a long time，we've believed that people become fat because they are lazy．
D．If you constantly feel tired or study too hard，you need to pay attention to your diet．
分析 本文讲述了研究人员通过在老鼠身上做实验，结果表明吃垃圾食品不仅会使人发胖，而且还会使人变懒．
解答 46．C 细节理解题．根据文章第三段Within three months，the rats in the second group were already much fatter than those on the healthy diet．And when researchers trained the rats to do simple tasks，they found even more differences between the two groups rather than weight可知经过三个月的实验后，吃垃圾食品的小白鼠已经比健康的小白鼠胖了很多；训练简单的动作，健康的小白鼠也比吃了垃圾食品的小白鼠表现的好，因此答案选C．
47．B 细节理解题． 根据文章第六段第一句But what about the possibility that the fat rats were less passionate about getting sugar water because they were already eating lots of sugar in their daily diet？可知研究者把纯净水给口渴的小白鼠喝，是为了测试增肥的小白鼠是否已经吸收了足够的糖分而对实验已经没有兴趣了．因此答案选B．
48．D 词义猜测题． 根据文意可知吃垃圾食品的小白鼠比之前变得懒惰的事实被研究者发现之后，这个实验并没有结束，因此答案选D．
49．C 推理判断题．根据文章倒数第二段But this study has proven the opposite to be true as well，which indicates that laziness and obesity are a"vicious cycle （恶性循环）"可知肥胖后和懒惰后是恶性循环的，即越胖就会越懒惰，而越懒惰就会越胖．因此答案选C．
50．B 细节理解题．根据文章第六段最后一句However，the results came out just the same可知研究者对吃垃圾食品的小白鼠进行测试的结果是一致的．所以答案选B．
点评 本题为研究类的阅读理解．这一题材的阅读理解是高考常考的内容，对考生来说有一定的难度，要求考生在通读全文把握大意的基础上，结合具体段落及语境做出正确的选择．
