Are the two liquids in thermal equilibrium if one is at 388 K and the other is at 288 K?

The two liquids are not in thermal equilibrium because thermal equilibrium occurs when two objects or systems reach the same temperature, and no net heat transfer takes place between them. In this case, one liquid is at 388 K, and the other is at 288 K. Since their temperatures are different, heat will flow from the hotter liquid (388 K) to the cooler liquid (288 K) until they reach the same temperature. Until that happens, they cannot be considered to be in thermal equilibrium.

Temperature is the key factor determining thermal equilibrium. Therefore, regardless of other factors like the mass of the liquids or their specific heat capacities, if their temperatures are not equal, they are not in equilibrium. Even when mixed, as suggested by one of the choices, without reaching the same final temperature first, they cannot achieve thermal equilibrium.