I think what ExpiredLink1 meant is what millstone says here [1], which I took to mean that although you don't need to know C before learning C++, psychologically it may help to know about C (i.e., that a language called C existed before C++ and that C++ is designed to be mostly backwards compatible with C), so that C++'s design choices don't seem as weird.

[1] https://news.ycombinator.com/item?id=8722655