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柔軟， じゅうなん
1. flexible, lithe, soft, pliable
2. calisthenics
柔软的；体操
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でなければならない， でなければいけない， でなければならぬ
1. having to be, must be, should be, ought to be
tbd
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
