首先来分析一下错句:Anyone did this must be caught...must be caught是谓语部分,根据本句的含义,主语应该是anyone, did this修饰anyone做定语,本句错误点是定语从句少了关系代词,也就是定语从句的引导词。改成Anyone who/ that did this must be caught.另外,提问者要注意的是anyone did this 是一个简单句,首先不管句意是否正确,从句子成分上来说,简单句不能做句子成分,而是从句才可以充当句子成分。