分析句子各个用逗号隔开的部分在句中成分,
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To be specific(插入语做独立成分),the number of passengers per year in Tokyo(名词短语作主语,中心词是number),the most of that in the six cities(名词短语做非限制性定语,补充说明number的地位),is 1927 million(第一个分句的系动词和表语),but the system in 1927 with a 155-kilometre route is neither the earliest nor the longest(but连接的第二个分句).