Question: Can we include static variable in header files.
If yes,Can other files can access it ?

Can we include static function in header files and use it in another files.

Can we pass static variable as function arguments ?suppose some function is there in header file header.h :

fun(static int a,static int b)

Answer: 
You can declare static variable in header files but this variable scope will only be that \*.c file in which this header file will be included.
Any name declared in the global namespace with specifier `static` has internal linkage. This means that the name is visible within the translation unit where it is declared.

So if a header with a declaration of a name with static keyword is included in several translation units then each translation unit will have its own variable with such a name.