Where is thermal equilibrium achieved between two objects

I believe the correct answer from the choices listed above is option C. Thermal equilibrium is achieved between two objects when both objects have the same temperature. This is the condition under which two substances in physical contact with each other exchange no heat energy. Hope this answers the question.

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).