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乗船， 上船， じょうせん
1. embarking (a ship), embarkation, boarding
2. ship (carrying someone)
登船，登船过程
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主に， おもに
1. mainly, primarily, mostly, largely, chiefly
主要地；首要地；大部分
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
