Answer:
A. Metal piece
A metal piece is a physical contaminant because it is a solid object that can inadvertently enter food products during processing, packaging, or handling. Physical contaminants are foreign objects that can cause harm if ingested and can include items such as metal fragments, glass shards, plastic pieces, or stones. In contrast, viruses (option B) are biological contaminants, while ammonia (option C) is a chemical contaminant. Copper vessel (option D) refers to a container made of copper and is not typically considered a contaminant unless it is corroded or degraded, leading to metal leaching into food or beverages.
