ANS:A - film

When the entire surface is exposed to nucleate boiling, the use of fins becomes advantageous, despite the large heat transfer coefficients already present in boiling liquids. In nucleate boiling, small bubbles of vapor form at discrete sites on the heated surface, enhancing the heat transfer process. The use of fins can further improve heat transfer by increasing the surface area available for heat exchange and promoting better mixing of the liquid around the surface. Fins disrupt the boundary layer of the fluid and facilitate the release of vapor bubbles, thereby enhancing heat transfer efficiency. While film boiling and transition boiling also occur under certain conditions, nucleate boiling typically offers the most efficient heat transfer. Therefore, when the entire surface is exposed to nucleate boiling, the addition of fins can provide further enhancement in heat transfer performance.