Correct option is C. (-6,1)
Option (c) is correct.
(a) $$-3+3=0$$
(b) $$-5+5=0$$
(c) $$-6+1=-5$$
(d) $$-8+8=0$$
By the above calculation, we can see that option c gives $$-5$$ while other options give $$0$$. Thus, option $$c$$ is different from all others.