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において， に於いて， に於て
1. at (a time or place), in, on
2. in (a situation, matter, etc.), on (a point), when it comes to, regarding, with respect to, in (terms of), as to, as for
3. on the part of, under the authority of, in the name of
在，于；在(一种情况、一件事等)中、在(一点上)、当涉及到、关于、就(方面)而言、至于、至于；由以下方面、根据以下方面的授权、以以下方面的名义实施
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役立つ， 役だつ， やくだつ
1. to be useful, to be helpful, to serve the purpose
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
