解析：
history n. 历史
a history teacher 历史老师
mystery n. 谜，神秘
No one could plumb the mystery. 没人能看破这谜。
gift n. 礼物
gifts for the children 给孩子们的礼物
解析：
teach v. 教，惩戒
The accident taught me a lesson I'll never forget. 这次事故给了我一个终身难忘的教训。
teach your grandma to suck eggs 班门弄斧
You can't teach an old dog new tricks. （自嘲）岁数大了，学不会了。#师者说#
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