Without facts,we can't form a worthwhile opinion,for we need to have factual knowledge upon which to base our thinking.请问在这个句子里，which后的不定式怎么理解？which引导定语从句有这种用法吗？
1. upon which to base our thinking=which to base our thinking upon 翻译：for we need to have factual knowledge upon which to base our thinking因为我们需要有能以此为基础，可建立我们思想的事实性的知识。2. 上述结构是比较常见的“疑问词+不定式”结构，此处它做后置定语，修饰knowledge。3. “疑问词+不定式”结构的具体讲解请参看我的另一回答：http://zhidao.baidu.com/question/57169770.html4. “疑问词+不定式”中如果是疑问代词，而且它做后面不定...
