Out of the following surfaces, the emis-sivity will be minimum for

ANS:B - concrete

Among the surfaces listed, the one with the lowest emissivity would typically be smooth glass. Smooth glass surfaces often have low emissivity values, especially when compared to materials like concrete, plaster, or aluminum foil. Emissivity is a measure of how efficiently a surface emits thermal radiation compared to a blackbody at the same temperature. Smooth glass surfaces tend to reflect more thermal radiation compared to absorb and emit it, resulting in lower emissivity values.