If x is the temperature of a system in Kelvin and y is the temperature of the system in °C, then the correct relation between them is

The relationship between the Kelvin and Celsius temperature scales is defined by a constant offset. The Kelvin scale is an absolute temperature scale where 0 K represents absolute zero, which corresponds to -273.15°C. To convert a temperature from the Celsius scale (y) to the Kelvin scale (x), one must add approximately 273.15 to the Celsius value. While the precise scientific conversion factor is 273.15, it is commonly simplified to 273 in many general science contexts and textbooks. Therefore, if x represents the temperature in Kelvin and y represents the temperature in degrees Celsius, the correct mathematical relation is x = 273 + y. This formula ensures that the freezing point of water (0°C) correctly aligns with 273.15 K.