根据短文内容及母提示完成所缺的单词。

     Adults smile less than children do in a day. 386 times less, in  fact. As a result, we are  becoming more

  and more unhappy and u __1__.

     All human beings are b __2__ to know how to smile. Children are s __3__ to smile up to 400 times a 

 day. For them, a smile comes from their h __4__  and pleasure. Unluckily, as we grow o __5__ , we

 smile less and less.

     "Adults only smile 14 times a day," says Jamb, a researcher. That means they only smile e __6__ two

 hours.

     "Life has so many problems that we  have forgotten all the r __7__ to smile,"she says.

     We just need to look for things that m __8__ us smile, for example, by smiling at a child in a

 supermarket.

      "Why are you afraid of a smile?" Jamb asks. Trying best to smile is the s __9__ of your happy journey!

  And anyway, s __10__ is a nice thing to do.