题目内容：

mr johnson has been a teacher for twenty years保持基本句意不变mr johnson＿a teacher twenty years＿两个下划线是空多谢了

优质解答

mr johnson has been a teacher for twenty years保持基本句意不变Mr johnso [became ]a teacher twenty years[ago.]

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不明白的再问哟,请及时采纳,多谢!