There are many reasons why C is the best programming language.
If I had to pick one language for all my programming, it would be C
If I could only teach one language to my child, an aspiring programmer, it would be C
If I had to write a program that would save the world, run a life support system and fly an airliner avionics or navigate guidance missile...etc., this is the language I would use.
C is the language that can be written in other languages.
C is the language that can program nearly all programmable devices around the globe.
C is the language that can create killer apps and games.
It is obsolete. It is also slow in terms of its development cycle. Even if the fundamental computer architecture remains the same, C could be the language that does all the work of the machine, while also pushing the limits.
C code is used often in C++, C#, and Objective-C programs that require speed and absolute control.