Combination of Resistors question from JEE Main 2024 (9 Apr, Shift 2)

Answer: (a)

1. Between the left and right corners of the diamond, the top, centre and bottom nodes are each joined by $R$ to both corners, so all three are at the same potential.
2. The two vertical resistors therefore carry no current; three paths of $2R$ remain in parallel: $\dfrac{2R}{3}$.
3. $R_{AB} = R + \dfrac{2R}{3} + R = \dfrac{8R}{3}$. So the answer is (a).