Is the relationship between kelvin and degrees celsius proportional? justify your answer in two different ways.

Yes I believe so
1 Kelvin = -273.15 degree Celsius

proportionality means that it has a sense of constants to it
so if I were to plug in a random Celsius value
In practicality if I then wanted it to Kelvin I just remember the simple ratio.

The next method is that 0k represents absolute 0 temperature
0c represents 0 degree of water (ice)
but at at 273.15k water exists in all three states simultaneously
Hope this helps bud!

Please if I can assist you further please let me know

There is no graph but what i can say is that 1 is the slope and that -2 is the y- intercept