KVPY SX SB Exam 2013 Question Paper

${\mathit{V}}_0={\mathit{V}}_{\mathit{i}}$ when no current flow through 1kΩ for negative values of ${\mathit{V}}_{\mathit{i}}$
i from ${\mathit{D}}_1=0$ (always)
i from ${\mathit{D}}_2=0$ upto 3V
So from 0 to - 3V, ${\mathit{V}}_{\mathit{i}}={\mathit{V}}_0$
from - 3 to - 4 V, ${\mathit{V}}_0=-3\mathit{V}$
For positive values of ${\mathit{V}}_{\mathit{i}}$
i from ${\mathit{D}}_1=0$ upto 1V
i from ${\mathit{D}}_2=0$ (always)
Hence 0 to 1V, ${\mathit{V}}_{\mathit{i}}={\mathit{V}}_0$
1 to 4 V, ${\mathit{V}}_0$ = 1 volt
Correct graph is (A)