What will be the output of the following C code?

#include <stdio.h>
int main()
{
    char str[10] = "hello";
    char *str1 = "world";
    strncat(str, str1, 9);
    printf("%s", str);
}

A. stdio.h B. iostream.h C. fileio.h D. files.h

A. fopen() B. open() C. writefile() D. createfile()

A. A built-in data type for files B. A file descriptor C. A file pointer D. A file structure

A. Use the 'filestatus' variable B. Check the return value of fopen() C. Use the 'fileopen' function D. Check the file's size