Explanation: When repairing circuit board assemblies, personal safety is the paramount concern. Wearing safety glasses protects your eyes from common hazards like flying solder, splashes of flux or cleaning chemicals, and small debris from scraping or drilling. Eye injuries can be severe and permanent, making prevention the highest priority. The other options describe useful repair techniques or tools, but they are secondary to personal safety: A) Clearing plated-through holes with a dental pick is a specific repair technique, not a universal "most important" step. B) Bridging broken traces with solder is a common repair method, but you wouldn't do this before ensuring your safety. D) Using a holding fixture is a good practice for stability and ease of work, but it doesn't protect you from immediate physical harm like safety glasses do. Always prioritize safety in the workshop.