Must every valid C program contain at least one preprocessor directive?

Introduction / Context:
Many codebases use numerous #include and #define lines, but the language does not require preprocessor directives in every program. Recognizing this helps clarify the boundary between the C language and its preprocessing step.

Given Data / Assumptions:

• We consider strictly conforming C programs.
• No assumptions about libraries beyond what the program itself uses.

Concept / Approach:
The C standard defines translation phases that include preprocessing, but it does not mandate that a program use any directives. A minimal program like int main(void){return 0;} contains no #include or #define and is perfectly valid. Preprocessing still occurs conceptually, but it has nothing to do if there are no directives.

Step-by-Step Solution:
Construct a trivial program with no headers and no macros.Compile it: the compiler parses, type-checks, and generates code without preprocessing work beyond trivial tokenization.Observe successful compilation and execution, proving no directive is required.

Verification / Alternative check:
Try compiling the minimal example on any standard-conforming compiler. It will compile and link (possibly requiring a runtime start-up library but not any header use).

Why Other Options Are Wrong:
“Correct” contradicts this simple counterexample; the claim about hosted implementations or optimization levels is irrelevant; requiring stdio.h is only necessary if you use its APIs.

Common Pitfalls:
Confusing common practice (always including headers) with language requirements; assuming preprocessing is a mandatory part of every source file’s content.

Final Answer:
Incorrect