Correct : b

To find the correct grid, we must check each option to see if it satisfies the shading constraints given for the rows (left numbers) and columns (top numbers). Let''s evaluate the options row by row to eliminate the incorrect ones.

Checking Row 1 (Target: 3 shaded cells)
All four options (i, ii, iii, iv) have exactly 3 shaded cells in the first row. We cannot eliminate any options yet.

Checking Row 2 (Target: 1 shaded cell)
Option (i) has 2 shaded cells in this row. ✗ Eliminate (i).
Option (ii) has 1 shaded cell in this row. ✓ Keep (ii).
Option (iii) has 2 shaded cells in this row. ✗ Eliminate (iii).
Option (iv) has 1 shaded cell in this row. ✓ Keep (iv).

Checking Row 3 (Target: 2 shaded cells)
We only need to check our remaining options, (ii) and (iv).
Option (ii) has 2 shaded cells in this row. ✓ Keep (ii).
Option (iv) has only 1 shaded cell in this row. ✗ Eliminate (iv).

Verifying Option (ii)
Now let''s verify that Option (ii) satisfies all remaining constraints to be absolutely sure.
Rows: 3 (Matches), 1 (Matches), 2 (Matches), 2 (Row 4 has 2 shaded cells - Matches).
Columns:
Col 1 has 2 shaded cells. (Matches target 2)
Col 2 has 2 shaded cells. (Matches target 2)
Col 3 has 2 shaded cells. (Matches target 2)
Col 4 has 2 shaded cells. (Matches target 2)

Everything matches perfectly.

Correct Answer: Option (ii) ✓