Given:
- Bulb 1: 25W, 220V
- Bulb 2: 100W, 220V
- Line Voltage: 440V

To find:
Which bulb will fuse when connected in series across the 440V line?

Explanation:
When bulbs are connected in series, the total voltage across them is divided between the bulbs according to their power ratings. The bulb with higher power rating will have a higher voltage drop across it.

To determine which bulb will fuse, we need to calculate the voltage drop across each bulb.

Calculating voltage drop across Bulb 1:
Using the formula:
Power (P) = Voltage (V) * Current (I)

Given that P1 = 25W and V1 = 220V, we can rearrange the formula to find the current:
I1 = P1 / V1 = 25W / 220V ≈ 0.1136A

The voltage drop across Bulb 1 can be calculated using Ohm's Law:
Voltage Drop (V1) = Current (I1) * Resistance (R1)

Since the resistance of a bulb remains constant, we can use the formula:
Resistance (R) = Voltage (V) / Current (I)

Given V1 = 220V and I1 = 0.1136A, we can find R1:
R1 = V1 / I1 = 220V / 0.1136A ≈ 1933.77Ω

Now, we can calculate the voltage drop across Bulb 1:
V1 = I1 * R1 = 0.1136A * 1933.77Ω ≈ 220V

Calculating voltage drop across Bulb 2:
Similarly, using the given values P2 = 100W and V2 = 220V, we can find I2:
I2 = P2 / V2 = 100W / 220V ≈ 0.4545A

Using Ohm's Law, we can find R2:
R2 = V2 / I2 = 220V / 0.4545A ≈ 483.87Ω

And the voltage drop across Bulb 2:
V2 = I2 * R2 = 0.4545A * 483.87Ω ≈ 220V

Comparing the voltage drops:
Since the voltage drop across both bulbs is the same (220V), both bulbs will not fuse. The correct answer is option 'D' (none of these).

However, if the voltage across the line were to increase to 440V (double the original voltage), the voltage drops across the bulbs would also double. In this case, the voltage drop across Bulb 2 would be higher than its rated voltage (220V), causing it to fuse. Hence, the correct answer would be option 'B' (only the 100W bulb will fuse) in that scenario.