在下列各句的每个空格内填上一个适当的、完整的单词，该词的首字母已给。
Tom felt too sleepy to keep a____ in history class.
I can't follow you. Can you e_____ it to me again?
Mary is s____ to be a good learner. Everyone thinks so.
Last month 10 persons were killed in the traffic a _____ .
He never does anything at home. He isn't a h____ boy. He's a lazy boy.
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