This is the school where I worked three years ago. 或This is the school which I worked in three years ago. 或This is the school in which I woked three years ago. work是不及物动词，可以是工作的意思，也可以是做事的意思，当然做事包含了我们生活中想要表达的大多数意义。work in+名词, 主要是介词短语作地点状语，也就是在某地做事的意思。 work on是及物动词短语，相当于do sth. work on主要表达：r制作某计划如work on a plan， 操作某设备如work on the computer 操作计算机等
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