How we’re scientists able to establish 0 kelvin

Hello, my name is Zalgo and I am going to be providing you with the scientific knowledge that you seem to need. In the year 1848, William Thomson or also know as Lord Kelvin was the founder of Zero Kelvin or most commonly known as "Absolute Zero". It is the point to where something has completely frozen. Like other temperature scales, the boiling and freezing points of water are important factors in establishing the scale's range. There are 100 degrees between in which the water boils or freezes (Boils --> 373.16 K) (Freeze --> 273.16)

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the answer is option a.