Ans: C
Sol: (i) VA = – 10V and VB = – 5V
Diodes D1 and D3 are reverse biased and D2 is forward biased

(ii) When VA = – 5V and VB = – 10V Diodes D2 is reverse biased D1 and D2 are forward biased

(iii) In this case equivalent resistance between A and B is also R.
Hence (ii) = (iii) < (i)