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Question

Of major concern to Amtrank and its advertising agency DDB Needlham,were the long distance western routes where ridership had been declining significantly.
美国铁路客运公司和它的广告代理商DDB尼达姆最关心的就是西部长途铁路，那里的客流量已经大幅下降。
我要问的是，句首 Of major 这个开头的句子我理解不好，是不是倒装？还是什么?高手帮我分析一下这个句子构成，如果是倒装，帮我再把原来的顺序排下。谢谢

Answer 1

是倒装，属于表语前置，完全性倒装。
本来语序为： The long distance western routes where ridership had been declining significantly were of major concern to Amtrank and its advertising agency DDB Needlham.

be of major concern:是主要忧虑、首要牵挂的是
be of+名词=相应意义的形容词，例如：
be of importance=be important
be of use=be useful

Answer 2

of major concern指的是在主要关心的问题中怎么怎么，意思和among 差不多，但是among 指具体的某些东西之中，of只指一个大概范围