在下列各句的空格内填上一个适当的单词，该词的首字母已给出。
1. I can't hear you. Can you read it a_______?
2. If you work hard, you will s________ in the end.
3. His mother often teaches him the i________ of working hard.
4. Peter f______ his math test last time. He was sad.
5. Though he is much too s_______, he tries his best to keep awake.
