Each graph below is the graph of a system of three linear equations in three unknowns. Determine whether each system has a solution and, if it does, the dimension of the solution space.

   
A.   B.   C.
   
D.   E.   F.
   
G.   H.   I.

(Click on a graph to enlarge it.)

In order to get credit for this problem all answers must be correct.