On the Celsius scale of temperature, absolute zero temperature is -273.15°C; option [D]. Absolute zero is the lowest possible temperature that can be theoretically reached, where particles of matter possess minimal thermal energy. At this temperature, the kinetic energy of particles is virtually nonexistent, and molecular motion ceases. Absolute zero serves as the foundation for the Kelvin scale, where it is defined as 0 Kelvin (0 K). The Celsius scale, commonly used in everyday temperature measurements, aligns with the Kelvin scale such that the interval between each degree Celsius is equivalent to one Kelvin. Therefore, -273.15°C on the Celsius scale corresponds to 0 Kelvin on the Kelvin scale. Absolute zero has profound implications in physics, serving as a reference point for understanding the behavior of gases, quantum mechanics, and the concept of entropy. Achieving absolute zero in practice is extremely challenging, requiring sophisticated cooling techniques, but its theoretical significance remains fundamental in the study of thermodynamics and the behavior of matter at extremely low temperatures.