Which law of thermodynamics allows us to define the concept of temperature scale:
First law of thermodynamics
Second law of thermodynamics
Zeroth law of thermodynamics
Third law of thermodynamics
The zeroth law is incredibly important as it allows us to define the concept of a temperature scale. If two systems are each in thermal equilibrium with a third, they are also in thermal equilibrium with each other.
Therefore, option (3) is correct.