d
(d) There is a decrease in volume during melting on an ice slab at $273K$.
Therefore, negative work is done by ice-water system on the atmosphere or positive work is done on the ice-water system by the atmosphere.
Hence option $(b)$ is correct. Secondly heat is absorbed during melting (i.e.$\Delta Q$ is positive) and as we have seen, work done by ice-water system is negative ($\Delta W$ is negative).
Therefore, from first law of thermodynamics $\Delta U = \Delta Q - \Delta W.$
Change in internal energy of ice-water system, $\Delta U$ will be positive or internal energy will increase.