Referring to the adjoining circuit which of the following is correct? 

Solution:

$\begin{array}{l}\mathrm{i}=1\mathrm{A},\therefore {\mathrm{V}}_{\mathrm{AC}}=4\times 1=4\mathrm{V},\mathrm{as}{\mathrm{V}}_{\mathrm{C}}=0,{\mathrm{V}}_{\mathrm{A}}=4\mathrm{V}\\ {\mathrm{V}}_{\mathrm{ED}}=2\times 1=2\mathrm{V},\mathrm{as}{\mathrm{V}}_{\mathrm{E}}=0,{\mathrm{V}}_{\mathrm{D}}=-2\mathrm{V}\\ \therefore {\mathrm{V}}_{\mathrm{B}}={\mathrm{V}}_{\mathrm{D}}+12=-2+12=10\mathrm{V}\\ {\mathrm{V}}_{\mathrm{BA}}=10-4=6\mathrm{V}\\ \therefore \mathrm{R}=\raisebox{1ex}{$\mathrm{V}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{I}$}\right.=\raisebox{1ex}{$6$}\!\left/ \!\raisebox{-1ex}{$1$}\right.=6\mathrm{\Omega };{\mathrm{V}}_{\mathrm{AE}}=4-0=4\mathrm{V}\end{array}$