The compilation of a C program goes through several stages:

Preprocessing:

• The preprocessor handles directives like #include, #define, and #ifdef.
• It replaces macros, expands header files, and processes conditional compilation.

Compilation:

• Converts the preprocessed C code into assembly language.

Assembly:

• Translates the assembly code into machine code (object file).

Linking:

• Combines multiple object files and libraries into a single executable.

Since preprocessing is the first stage in this sequence, the correct answer is (C) Preprocessing.