5

This しなければなりません just means "must", "need to", "have to". And that's the only meaning of しなければなりません. この会に来たインドの人は「日本にいろいろ教えてもらって、早く空気をきれいにしなければなりません」と話していました。 An Indian person who came to the meeting said, "[I] have to make the air (of India) clean after Japan taught a lot of things to [me]." An Indian person who came to the meeting said, "[We ...


3

You don't really have to do anything special- just put the final verb (adjective) in the past tense. 学校まで走らなければならない - I have to run to school 学校まで走らなければならなかった - I had to run to school This works with all three of the constructions you mentioned. ならない = ならなかった だめ(だ) = だめだった いけない = いけなかった Of these, I see ならなかった the most by far, but the other two ...


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