The easiest way to solve this is by making simple addition problems from all of the sets of numbers.
4 + 4 = 8
4 + (-4) = 4 - 4 = 0
-4 + (-4) = -4 - 4 = 8
4 + 0 = 4
So, you know that B: 4 degrees Celcius and -4 degrees Celcius have a sum of 0 degrees Celcius.