That is all加There is all to it== That is all (that) there is to it 变成了定语从句. 又如：That is all.加I want to say all ========That is all (that) I want to say. 定语从句中省去了that.明白了吗?there is to it 是什么意思呢That's all there is 中文：就这件事情来说，你/我知道的就这么多了。to it ==关于这件事情。