graph c is the right answer 
Explanation:
by solving the linear equation with one variable
we have constant value for y= - 3
so 
x changes and y remain same 
as we know 
the 2nd coordinate show y axis in order pair 
so we have to look 
for change of x but no Change in y coordinate in order pair
which is in graph c
(0,-3),(1,-3)
so graph c is the answer
i hope you get it