how the tributaries of an almost parallel structur--almost前面为什么加an??

Almost everyone knows the meaning of Mr., Mrs. an

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\u300c\u82f1\u8bed\u8d34\u58eb\u300dalmost\u548cnearly\u6709\u533a\u522b\u5417\uff1f\u7b54\u6848\u5f88\u7b80\u5355\u3002

除非特殊情况，句中出现单数形式的可数名词（structure)的时候，前面都需要加冠词(a/an)或定冠词（the/this/that)。
这句的almost parallel是修饰structure的定语，所以前面要加an

怎么几乎平行的结构流失的附庸国到谷里

扩展阅读：this war of mine ... the owl lived in a tree ... trouble is a friend ... pokemon go ... have contribute to ... a dance of fire and ice ... how to secretly ... there is no game ... hide the truth ...