Each graph below is the graph of a system of three linear equations
in three unknowns of the form A \vec{x} = \vec{b} .
Determine the dimension of the null space of the matrix A .

(Click on a graph to enlarge it.)

A. |
B. |
C. |
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D. |
E. |
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(Click on a graph to enlarge it.)

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