英语高手帮忙看一下这三道题

第一句是强调句。不是定语从句。
第二句是where引导的定语从句，where是关系副词。表示地点，这里之所以区别于第一句不用that表示强调句有一个判断的绝巧。 强调句的句型在去除了it was和that这两个部分以后还是可以组成一个完整的句子。比如第一题里面去了it was和that后：
when he took a job in a company，he began to learn English.
并不影响句子的意思。

第三句的话还是where引导的定语从句，也可以换成是which，但是前面要加介词in：
It was the park in which tom lost his watch.
注意，这里不能用that，因为that不能放到介词后面，有介词的话只能用which。

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强调句句型
1、陈述句的强调句型：It is/ was + 被强调部分（通常是主语、宾语或状语）+ that/ who（当强调主语且主语指人）+ 其它部分。
e.g. It was yesterday that he met Li Ping.

2、一般疑问句的强调句型：同上，只是把is/ was提到it前面。
e.g. Was it yesterday that he met Li Ping?

3、特殊疑问句的强调句型：被强调部分（通常是疑问代词或疑问副词）+ is/ was + it + that/ who + 其它部分？
e.g. When and where was it that you were born?

4、强调句例句：针对I met Li Ming at the railway station yesterday.句子进行强调。
强调主语：It was I that (who) met Li Ming at the railway station yesterday.
强调宾语：It was Li Ming that I met at the railway station yest