题目内容：

i'm sorry i ___ that you didn't understand what i said. now let me try to speak again.
A don't know B didn't know
答案是B,句子有现在时态又有过去时态, 如何理解选择B?多谢!

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9． 【72653】 -- Sorry,I didn't catch what you said． -- _____ A． That's fine． B． Don't mentio 2016-12-13