Final answer:
The endothermic process among the given options is ice melting (option C).
Step-by-step explanation:
An endothermic process is a process that absorbs heat from its surroundings. In the given options, the only endothermic process is ice melting (option C). When ice melts, it requires heat/energy from its surroundings in order to change from a solid to a liquid. The other options, boiling soup (option A), water freezing (option B), and mixing hydrochloric acid and barium hydroxide (option D), are all exothermic processes as they release heat to the surroundings.