conio.h is an ANSI standard header file.
B
Correct answer
Explanation
conio.h (Console Input/Output) is NOT an ANSI/ISO standard C header file. It was originally developed for DOS and Microsoft operating systems. Functions like clrscr(), getch(), and getche() from conio.h are platform-specific and not part of the standard C library, which uses stdio.h for input/output operations.