她将去北京但我不知道她怎么去。

(4)定语从句中的省略

定语从句中也常使用不定式作为省略的手段;当用as引导非限制性定语从句时，常省略系动词。

例1：All tests require a potential candidate with whom (the tests) to compare DNA.

所有的测试都需要一个潜在的对象，从而可以将DNA与其比较。

例2：He gave the same answer as (he had given) before.

他给出的答案和以前一样。

三、真题举例

However , it has been found that even people insensitive to a certain smell at first can suddenly become sensitive to it when exposed to it often enough . (05,完型)

【重点词汇解析】insensitive，adj. 感觉迟钝的;expose，vt. 使曝光、揭露、显示