The light bulbs $\mathrm{A}$ & $\mathrm{B}$ in the following circuits are identical. When the switch is closed 

• A

  Intensity of bulb $\mathrm{A}$ increase
• B

  Intensity of bulb $\mathrm{A}$ decrease
• C

  Intensity of bulb $\mathrm{B}$ increase
• Correct answer
  D

  Nothing changes

Solution

After closing of switch voltage across $\mathrm{A}$ & $\mathrm{B}$

remain same
$\therefore$ Nothing change

Hence, the correct answer is option: 'D'.