The correct answer is C) Wire brush. A wire brush is the appropriate hand tool for preparing a metal surface with significant pitting for the application of primers and finish coats. The wire bristles can effectively remove rust, scale, and other surface contaminants from pitted areas, preparing the surface for proper adhesion of the coatings. The other options are not as well-suited for this task. A chipping hammer (A) is better suited for removing larger, thicker deposits, while sandpaper (B) may not be able to effectively clean out the pitted areas. A hand scraper (D) is more commonly used for smoothing and leveling flat surfaces, rather than addressing pitted areas.