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を
1. indicates direct object of action
2. indicates subject of causative expression
3. indicates an area traversed
4. indicates time (period) over which action takes place
5. indicates point of departure or separation of action
6. indicates object of d...
表示动作的直接对象；表示经过的场所；表示离开或分开的点
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入れ替える， 入れ換える， 入れかえる， 入れ代える， いれかえる
1. to replace, to substitute, to shift, to change places
替换，替代，转换，调换位置
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ないと， 無いと
1. have to (verb), must (verb)
2. is indispensable, absolutely necessary
tbd