990809语法请教

_____ at a river ford on the Donner Pass route to California, the city of Reno grew as bridges and railroad were built.

(A) Settle

(B) To settle

(C) It was settling

(D) Having been settled

为什么不用hasing been settled呢?

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麻烦高手回答

这问题实在有点难，呵呵。。先看一下整个选项的话，其他几个是可以排除掉的。

在独立结构中，出现表时态的助动词使用原形，就像being，而不用was，is，were，are等等。have看成是has、 have的原形形式，所以用have。

不过这个不会是ETS的考点。如果出现being settled 和having been settled或者settled 出现比较的话，就更离谱的难了，那时需要根据句子揣摩一下。不过不会在托福里面考到。