b
As the P.D.

between \(4 \Omega\) and \(3 \Omega\)

(in parallel), arc the same, \(4 \times 1\) amp \(=3 \times i_{1} \Rightarrow i_{1}=\frac{4}{3} A\)

Total resistance of \(4 \Omega\) and \(3 \Omega=12 / 7 \Omega\)

Current in \(M Q P\) (upper one) \(=1+\frac{4}{3}=\frac{7}{3} A\) \(\therefore \quad P . D .=\frac{12}{7} \times \frac{7}{3}=4 V\)

Current in \(M N P=\frac{4}{1.25}=\frac{4 \times 4}{5}=\frac{16}{5} A\)

\(\therefore \quad\) P.D. across \(1 \Omega=\frac{16}{5} A \times 1 \Omega=\frac{16}{5}\) volt

\(\Rightarrow\) P.D. across \(1 \Omega=3.2\) volt.