Which indicates that thermal energy is no longer being transferred from boiling water to a mug? The mug and the water lose all thermal energy. The water is hotter than the mug. The mug is hotter than the water. The water and the mug are the same temperature.

The answer is ‘The water and the mug are the same temperatures’. This means that the two bodies have reached thermal equilibrium. This two are thermally connected bodies through a diathermal connection-meaning only heat (not matter) can be transferred between the two.