17. It's a theory to which many economists subscribe, but in practice it often leaves railroads in the position of determining which companies will flourish and which will fail.

【分析】并列复合句。but连接两个并列的分句。第一个分句的主干是It's a theory, which引导的定语从句修饰theory;第二个分句的宾语补足语in the position of...包含两个which引导的从句，均作determining的宾语。
【译文】许多经济学家对这种理论表示赞同，但实际上这样常常要由铁路部门去决定哪些公司兴旺，哪些公司破产。
【点拨】l)subscribe to的含义有“订阅；同意，支持；捐赠”，在本句中显然是“同意，支持”之意。2)fail在此处不是“失败”的意思，而是指“（公司的）破产，倒闭”。

18. "Do we really want railroads to be the arbiters of who wins and who loses in the marketplace?" asks Martin Bercovici, a Washington lawyer who frequently represents shippers.

【分析】多重复合句。本句是个完全倒装句。谓语是asks,主语是 Martin Bercovici，其后的 a Washington lawyer …是其同位语，其中包含who引导的定语从句，修饰 lawyer；引号内的句子是宾语。宾语从句的主干是Do we really want railroads to be the arbiters …。介词短语of who wins and who loses in the marketplace 作 arbiters 的后置定语，其中who引导的两个从句作of的宾语。
【译文】“我们真的要让铁路部门成为市场中成败的仲裁者吗？”马丁·贝尔科维希问道，他是一名经常作为发货商代理人的华盛顿律师。