$(A)$ the elecric field at $O$ is $6 K$ along $O D$
$(B)$ The potential at $O$ is zero
$(C)$ The potential at all points on the line $PR$ is same
$(D)$ The potential at all points on the line $ST$ is same.
$V _0=0$
Potential on line $PR$ is zero Ans. $(A), (B), (C)$



