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.