Time files when you play on your smartphone.But when you get down to the real business of work and study，one hour feels like a year.Why are we so attracted by smartphones but easily bored by studying？
   It all boils down to something small and hard to see：dopamine（多巴胺）.Dopamine is a "pleasure chemical" that makes people feel good.Our brains give it out when we eat yummy food，after we exercise or when we get a prize.
   Compared with studying，playing on smartphones causes our brains to give out more dopamine.For example，checking your phone for a text leads to a 400 percent increase in dopamine.But why？
   When we visit social media，we don't know what we'll see next，or who will give opinions about things we post（發(fā)布）.This "magic of maybe"，makes the dopamine system active.We get excited wondering if we have messages from our friends.When our expectations（期待）are met，dopamine is given out.
   And to find more dopamine，we continue checking our phones.Studying doesn't provide such magic.Without this excitement，we get bored much more easily.
   Can we do something to change that？According to scientists，apps can become less attractive if we turn off notifications（通知）or change the screen colors to black and white.We can also set time limits on apps to avoid using them too much.
   As for studying，you could check your progress daily or weekly and reward yourself for it，said Daniel Wong，writer of The Happy Student.You could also search for interesting topics connected with your textbook.Use what you've learned to make an influence in the real world.This will make knowledge much more interesting to learn.

（1）According to the article，what are students like when they study？

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C

A．They get very attracted.
B．They are getting happier.
C．They feel time pass more slowly.
D．Their brain give out more dopamine.
（2）What might the phrase "boils down to" mean in Paragraph 2？

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D

A．works out.
B．turns out.
C．leads to.
D．results from.
（3）When do people have more dopamine？

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C

A．When they know what will happen next.
B．When they stay in a familiar environment.
C．When their expectations are met.
D．When they face fewer unknown things.
（4）What is Paragraph 4 about？

D

D

A．It introduces a way to get more messages from our friends.
B．It gives an example of spending time happily on social media.
C．It describes how scientists discover the way dopamine works.
D．It explains why playing on smartphones causes more dopamine.
（5）Which of the following might Daniel Wong suggest to make learning interesting？

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C

A．Setting time limits on everything you do.
B．Stopping playing and finding more interests in real life.
C．Using what you learn from textbooks to do things in real life.
D．Reading the interesting part in your textbooks before reading the others.