Answer:
Thermal energy by conduction
Step-by-step explanation:
When cold water is poured into a glass, we have two objects in contact each with a different temperature. Therefore, the system is.not at equilibrium.
For the system to reach equilibrium, heat always transfers from the object with high temperature (glass in our case) to the object with less temperature (cold water in our case). This transfer keeps occurring until both objects have the same temperature.
Now, since the two objects are in direct contact, therefore, heat would transfer by conduction
Hope this helps :)