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生存， せいぞん
1. existence, being, life, survival
tbd
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必要， 必用， ひつよう
1. necessary, needed, essential, indispensable
2. necessity, need, requirement
必要的，必需的，必不可少的，不可缺少的；必要性，需要，要求
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
に
1. at (place, time), in, on, during
2. to (direction, state), toward, into
3. for (purpose)
4. because of (reason), for, with
5. by, from
6. as (i.e. in the role of)
7. per, in, for, a (e.g. "once a month")
8. and, in addition to
9. if, although
tbd
