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ただ， タダ， 只， 唯， 徒， 但， 常
1. ordinary, common, usual
2. free of charge
3. unaffected, as is, safe
4. only, merely, just, simply
5. but, however, nevertheless
但是，尽管如此；通常，一般情况下；免费；只、仅仅
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皮， かわ
1. skin, hide, pelt, fur
2. rind, peel, husk, bark
3. shell, sheath, wrapping
4. mask (hiding one's true nature), seeming
皮
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
