首先,这句话就是错误的.老外不会理解你在说什么.正确的句子应该是：
I’ll present the facts on which my opinion is based.
on which my opinion is based 的确是定语从句,修饰 facts.要是像你说的那么简单我就犯不着提问了,这终句型很常见啊 如we need to have it on which to base our policy,用从句就不用说了,地球人都知道,高手讲讲不用从句的情况你是在国内的什么书上看到的这种句子吧？在说英语的国家真的没人这么用， on which to base our policy 或许在写作中还可以见到，但 on which to be based my opinion，这种句子，真的是“天外飞仙”，只有中国人才见过吧？on which to base our policy那就算是这句,请告诉我这是什么从句?是定语从句。