A phase change (like going from a solid to a liquid) is an example of an increase in potential energy. The temperature does not change due to this factor along. So A and B are both incorrect because they both want to change the temperature.
That leaves only C and D to consider.
H2OI_solid + heat ==> H2O_liquid
The language you have provided is represented by the equation shown above. The answer is C. It is all that could have happened.