Which choice is an include guard for the header file mylib.h?
:
#ifdef MYLIB_H #define MYLIB_H // mylib.h content #endif /* MYLIB_H */
#define MYLIB_H #include "mylib.h" #undef MYLIB_H
#ifdef MYLIB_H #undef MYLIB_H // mylib.h content #endif /* MYLIB_H */
#ifndef MYLIB_H #define MYLIB_H // mylib.h content #endif /* MYLIB_H */