阅读下面短文，根据汉语或首字母提示，在每个空格内填入一个适当的英语单词。所填单词要求意义准确，拼写完整、正确。

Why are we always tired, do you know? F__71___, if we can’t sleep well, we will be tired. But we are often too busy. If we can’t    72    (完成) our work in the day, we must do it at night. We go to bed l   73    and get up early. So we can’t sleep well. Most people need at least eight h   74    and some even more to sleep. If we sleep for    75   (仅仅) five or six hours at night, we will be tired.

Second, when we are ill, we will be tired. But we don’t know we are ill. So if you are always tired, maybe you are not so    76   (健康的). You should go to see a doctor.

Third, p   77  （也许）you can’t eat some kinds of food like eggs, nuts, meat, or chocolate. If you are ill and tired after eating some food, please stop e   78   them to see if you are well.

At last, if the air around you isn’t clean, you will feel tired. So please open the    79   (窗户) or go out for a walk and you will feel    80   (更好的).

71. __________ 72. __________ 73. __________ 74. __________ 75. __________

76. __________ 77. __________ 78. __________ 79. __________ 80. __________