• Step 1: Ground Scale Conversion:

$$\text{Photo scale} = 1 : 10,000 \implies 1\text{ cm on photo} = 10,000\text{ cm} = 100\text{ m on ground}$$ $$1\text{ cm}^2\text{ on photo} = 100\text{ m} \times 100\text{ m} = 10,000\text{ m}^2 = 1.0\text{ hectare}$$

• Step 2: Area Represented by a Single Dot:

$$\text{Grid density} = 20\text{ dots/cm}^2$$ $$\text{Area per dot} = \frac{1.0\text{ ha}}{20\text{ dots}} = 0.05\text{ ha/dot}$$

• Step 3: Total Flooded Ground Area:

$$\text{Total Area} = 120\text{ dots} \times 0.05\text{ ha/dot} = 6.0\text{ hectares}$$

• Conclusion: The flooded ground area is 6 ha. (Correct answer: Option 2)