In standard state, the non spontaneous reaction is

 Water exists in liquid state naturally at standard state $25°\mathrm{c}=298\mathrm{k}$. Hence freezing of ${\mathrm{H}}_2\mathrm{O}$ at $298\mathrm{k}$ is non-spontaneous as ice will absorb heat from surroundings thereby gets converted to the liquid state as it is a natural process of is irreversible. 

Hence the correct answer is (C) Freezing of water.