Which of the following is a header file of C?
Stdlib.h is not a header file of C.
stdlib.h is the header of the general purpose standard library of C programming language which includes functions involving memory allocation, process control, conversions and others. It is compatible with C++ and is known as cstdlib in C++. The name "stdlib" stands for "standard library".
A header file is generally used to define all of the functions, variables and constants contained in any function library that you might want to use.