A heavy iceberg melts at the bottom rather than the top, because

A heavy iceberg melts at the bottom rather than the top because the melting point decreases due to the pressure of the lower layer being higher (B). As the weight of the iceberg compresses the lower layers, the pressure increases, lowering the melting point of ice according to the principle of pressure melting. This causes the ice at the bottom to melt first, despite the fact that the temperature may be colder at greater depths. Options (A) and (C) are incorrect as they do not accurately explain the phenomenon. While the temperature gradient within the iceberg may play a role, it is primarily the pressure-induced decrease in melting point that causes bottom-up melting in heavy icebergs. Therefore, option (B) provides the most appropriate explanation for why heavy icebergs melt at the bottom.