The correct answer is D) Steam clean areas obstructed by structural members. This is correct because steam cleaning areas obstructed by structural members is not typically required in preparing a hold for reception of a bulk grain cargo. The key requirements are to remove residue of any previous cargo (A), spray or fumigate to eliminate any insect colonies (B), and remove loose rust and scale (C) to ensure the hold is clean and free of contaminants that could affect the new cargo. Steaming cleaning obstructed areas, while sometimes done, is not a mandatory step in the standard hold preparation process for bulk grain cargoes. The other answer choices (A, B, and C) describe typical and necessary actions to ready a cargo hold, which is why they are not the correct answer to what is "usually NOT required".