日常英語(yǔ) not know the time of day 一問三不知

“一問三不知”，指怎么問都不知道（say "I don't know" to every question），很糊涂或很無(wú)知。可以翻譯為“be entirely ignorant; not know a thing”。與英文慣用語(yǔ)“not know the time of day”意思相近，表示“to be completely unintelligent, daft, or not alert”。

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例句：

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別問他了，他總是一問三不知。

Don't ask him any questions. He never knows the time of day.