C, because I can find a compiler or interpreter for other language written in C (I may need to run a few steps to get there), and thus work around your silly and nonsense question. Seriously, I use multiple languages because there is no one true language to rule them all. I use C++ for problems where bash would be wrong, and bash where C++ would be wrong. And some python, cmake, lua mixed in for good measure. I'm looking at Rust to add (rust doesn't like the way our system designed so it is hard to figure out how to implement it)