Anything that prompts the release of dopamine in the brain brings pleasure.For example，cocaine and coffee both release dopamine in the brain.The release of dopamine in the front half of our brain is accompanied by a real smile.But can this process be reversed？What about putting on that happy face？Can the simple act of smiling bring pleasure？Yes.

　　When we smile，fake or real，the contraction of the facial muscles slightly distorts(扭曲)the shape of the thin facial bones.This slight distortion in their shape leads to an increase in blood flow into the brain and then increases the release of dopamine.As a result，walking around all day with a smile on your face will make your mood happier.Not only will you be happier but your smile might lead to the release of dopamine in someone else’s brain—now that truly shows the power of a smile.

　　真笑和假笑都能给我们带来快乐。

　　5．When we smile sincerely，______.

　　A．bones in our face become thin

　　B．muscles in the face become smaller

　　C．the brain’s dopamine neurons stop working

　　D．the brain’s motor cortex starts to work

　　解析：细节理解题。根据第二段The muscles that attach to these bones become smaller when we are happy or when we want to laugh可知，答案为B项。

　　答案：B

　　6．The underlined word“prompts”in Paragraph 4 can be replaced by“______”．

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