Final answer:
Absolute zero corresponds to 0 K (kelvins) in the Kelvin temperature scale, -273.15°C in the Celsius scale, and �459°F in the Fahrenheit scale; therefore, the correct answer is 0° Kelvin.
Step-by-step explanation:
Understanding Absolute Zero Absolute zero is the theoretical lowest possible temperature where all molecular motion ceases. In the Kelvin temperature scale, which is an absolute scale used frequently in scientific contexts including astronomy, this corresponds to 0 K. It's important to note that one should just say 'kelvins' and not 'kelvin degrees' when referring to this scale. On the Celsius scale, absolute zero is at -273.15°C. It's theoretically the point at which no thermal energy can be extracted from matter as all molecular movement stops. The Fahrenheit equivalent of absolute zero is approximately -459°F. While it is not actually possible to reach absolute zero due to the behavior of gases and other physical limitations, it serves as a vital concept in understanding the limits of cold temperatures.
The correct answer to the question 'Absolute zero is?' is option 5) 0° Kelvin.