1. Analyze the V-I Graph:
Looking at the characteristic graph for device D, for any voltage greater than 1.0 kV, the current saturates and remains constant at:
I = 10 mA = 0.01 A

2. Calculate Voltage Drop Across Resistor:
The circuit has a resistor R = 300 kΩ.
V_R = I × R
V_R = 0.01 A × 300,000 Ω = 3000 V = 3.0 kV

3. Apply Kirchhoff’s Voltage Law (KVL):
The total battery voltage is 5.0 kV.
V_battery = V_R + V_device
5.0 kV = 3.0 kV + V_device
V_device = 2.0 kV

4. Verification:
At 2.0 kV, the graph confirms the current is indeed 10 mA. The assumption holds.