SAT语法题一道peter the great totally changed the landscape of St.

　　这里不是过去完成时的问题系,而是属于 it 指代不明的错误.
　　Peter the great totally changed the landscape of St.Petersburg 和 (and it had been) a swamp unusedby previous tsars 是并列句.第一分句中的宾语是 landscape of St.Petersburg,其中landscape 指事物,St.Petersburg 指地点,都可以用代词 it 指代.所以,第二分句的主语 it 属于指代不明.it had been a swamp 既可以理解为 the landscape had been a swamp（这里的地貌曾经是一片沼泽）,也可以理解为 St.Petersburg had been a swamp （圣彼得堡曾经是一片沼泽）.

Peter (the great totally changed the landscape of St. Petersburg ) has been a swamp unused by previous tsars.

改成　St. Petersbur, which had been a swamp unused by previous tsars.
要用定语从句，否则就是句子杂揉

前后主语不一致。
前句主语是Peter the Great，后句主语是it（the landscape of St. Petersburg），即前句的宾语。
这种情况不能简单用连词and连接，而应该采取直接断为两句或者采用定语从句的办法。

两句话没有逻辑关系啊 后面的句子就是单纯的是过去发生的事情对现在依然有影响 用现在完成时