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なんです， なのです
1. it is assuredly that ..., can say with confidence that ...
〜んです句型；可以肯定地说……，可以有把握地说……
は
1. indicates sentence topic
2. indicates contrast with another option (stated or unstated)
3. adds emphasis
指示句子的主题；表示与另一选项（无论是否明确提及）形成对比；表示强调
が
1. indicates the subject of a sentence
2. indicates possession
3. but, however, (and) yet, though, although, while
4. and
5. used after an introductory remark or explanation
6. regardless of ..., whether ... (or not), no matter ...
7. indicates a des...
tbd
