Answer:
4. thermal
Step-by-step explanation:
When there is a difference in the temperatures of an object and the environment, heat is transferred. The transfer of heat is the form of transfer of thermal energy. The energy from the hotter object gets transferred to the cooler object. This is the process of transfer of heat. In this process, the object that is hotter is likely to get cool and vice-versa.
As per the given statement, when an ice cube is placed in a weaker of water, the transfer of thermal energy will take place. Here, ice cube is the cooler object and the beaker of water is hotter.