B. All the same
Explanation
Total voltage of a parallel circuit has the same value as the voltage across each branch:
in the image, the voltage across R1 is the same as the voltage across R2,
Step 1
Increasing the voltage increases the brightness of the bulb. it means the brigthness depends on the voltage (also the brigthness depends on the current), so as the potential difference is the same, we can conclude the brigthness is the same, In a parallel circuit the voltage for each bulb is the same as the voltage in the circuit. Unscrewing one bulb has no effect on the other bulb.
so the answer is
B. All the same
I hope this helps you
