In the circuit shown in figure, the potentials of B,C and D are :

Potential at O is zero being earthed.Applying Kirchhoff’s second lawi(1+ 2 + 3) =12 - 6 or i = 1AVA−VD=(1+2+3)×1=6VVA−VB=1×1=1VVA−VC=(1+2)×1=3VAlso, VA−VO=12V or  VA=12VThus, VD=12−6=6VVB=12−1=11V,VC=12−3=9V