1) C done in C++ is not as fast as C done in C, the C++ compiler actually has to translate C into C++, or else it just calls the C compiler to handle the C code.
2) Systems level programming is done in any compiled language, Solaris is Java, windows is C++, every other os in C.
[ yes, java has the jit, but it can be compiled into ececutables and stored that way. ]
3) most rapid execution languages, like python, perl, php .. are actually WRITTEN in C.
[ download the sources and check for yourself, I know PHP* and Python are both written in C. }
* PHP's Zend engine being an exception, it is written in Java.