As we saw in the preceding question (selection C) this matrix is not reduced because the leading entry in row 2 does not have its column cleared:

	1	1	5	0	7
	0	1	1	0	4
	0	0	0	1	0
	0	0	0	0	0

We therefore need to clear that column by pivoting. The only row that needs to change is Row 1, so we obtain

1 1 5 0 7 R1 R2 0 1 1 0 4 0 0 0 1 0 0 0 0 0 0

1 0 4 0 3 0 1 1 0 4 0 0 0 1 0 0 0 0 0 0

Now you can check that the matrix on the right is row-reduced.