Electrical Power & Heating Effect question from NEET 2019

Answer: (b)

1. Section A's three bulbs are in parallel, and so are section B's; the two sections are in series.
2. All glowing: $R_1 = \dfrac{R}{3} + \dfrac{R}{3} = \dfrac{2R}{3}$.
3. Two in A, one in B: $R_2 = \dfrac{R}{2} + R = \dfrac{3R}{2}$.
4. $P = E^2/R \Rightarrow P_1 : P_2 = R_2 : R_1 = \dfrac32 : \dfrac23 = 9 : 4$.
5. So the answer is (b) 9 : 4.