At the risk of feeding a possible troll, FreeBSD is written in almost entirely in C. There is some C++ for things, but not much. Furthermore, there's also platform dependent Assembly Language for the real low-level stuff that is machine dependent. Things such as segmentation, virtual memory to physical memory mapping, threading and context switching, etc. If you want to develop on FreeBSD, C is definitely a requirement. However, there are other languages that are availiable for application development. We all know about C and C++, but there's also D, Python, Ruby, PHP, Perl, Pascal, Forth, Ada, Lisp, Fortran, Cobol, Java, Shell Script, Basic, etc.... And those are the ones that I am aware of. I'm sure there are others. So my suggestion to you is pick your poison and go with it.
