A and C show y = -x
Step-by-step explanation:
y = -x is the diagonal passing through the origin that goes downwards from left to right.
The x and y coordinates of each point are negatives of each other, e.g. (2,-2); (-3,3) etc.
In this question, we can see that both A and C have x and y coordinates that are negatives of each other, while B does not.
Hope this explains it :)