I believe that the answer is A.
Every point shown on the graph is a solution of the equation because when the coordinates of the points are substituted into the equation, the equation is true for all the points.
because if we take the points (0,3) from the picture and put in them in the equation, so it will gives you;
3x – 2y = –6
3*0-2*3=-6
-6=-6
hope you understand it :)