Step 1: Understanding the figure.
The given diagram represents a total area of $10 \text{ km} \times 10 \text{ km}$ divided into different land-use categories represented by symbols A, B, C, and D. Each symbol corresponds to a specific pattern shown in the legend.
Step 2: Estimating areas visually.
By carefully observing the figure, the unshaded region (B) occupies the maximum number of grid squares and hence represents the largest land-use area.
Step 3: Identifying the second largest land-use.
Among the remaining patterns, land-use D (dense diagonal shading) covers more grid blocks than A and C. Its spatial spread across multiple blocks makes it the second largest area after B.
Step 4: Eliminating other options.
(A) C: Covers fewer grid squares than D.
(B) A: Occupies smaller scattered regions.
(C) B: This is the largest area, not the second largest.
Step 5: Conclusion.
Therefore, the land use that covers the second largest area is D.