Which statement defines the temperature of a sample of matter?

Temperature is a measure of the average kinetic energy of the particles in the sample. This is the statement that defines the temperature of a sample of matter.

The temperature of a system is defined simply as the average energy of microscopic motions of a single particle in the system per degree of freedom.

The microscopic motions in a solid matter is the principal vibrations of the constituent atoms about their sites. In an ideal monoatomic gas, the microscopic motions are the translational motions of the constituent gas particles. In multiatomic gases, aside from translational motions, vibrational and rotational motions are included in the microscopic motions.