ANS:A - remove hydrogen.

Phosphorus is added to a copper melt primarily to deoxidize the metal. When copper is melted, it can absorb small amounts of oxygen, which can form oxides that can negatively affect the properties of the metal, such as its mechanical properties and surface quality. Phosphorus acts as a deoxidizing agent, reacting with oxygen present in the melt to form phosphorus oxide, which is then removed as slag, leaving behind a purified copper. While phosphorus can help remove hydrogen from molten copper, it is not typically added specifically for that purpose. Similarly, phosphorus can contribute to improving fluidity and reducing shrinkage in certain circumstances, but its primary role in copper metallurgy is deoxidization.