(c) which is greater, 300 kelvins or 25 degrees celsius? show your work.

There are several information,s already given in the question. I am answering the question based on the information,s provided. 
We already know that 
0 degree centigrade = 273.15 degree kelvin
Then
25 degrees Celsius = 273.15 + 25 degrees kelvin
                                = 298.15 degrees kelvin.

From the above deduction, we can conclude that 300 degrees kelvin is greater than 25 degrees Celsius.