前一个polluted为过去分词,属定语从句中的谓语,后一个为过去式,属主句的谓语.句意为:曾被污染的那条河污染了另一条河。

The river which had been polluted polluted another one.

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本句是并列句，前一个分句中，“if”引导条件状语从句，主句主语“it”指代“the tradition of ambition”。 后一个分句中“who”引导一个定语从句修饰“people”，“the educated not least among them”是“people”的补语。

If the tradition of ambition is to have vitality, it must be widely shared; and it especially must be highly regarded by people who are themselves admired, the educated not least among them。

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