In the given part of a circuit, the potential at point B is zero. Then the potentials at A and C respectively are
 

We know that the current flows through the resistor between A and B

So, V_A — 1.5 x 1 = V_B

$\begin{array}{l}{\mathrm{V}}_{\mathrm{A}}-1.5=0\\ {\mathrm{V}}_{\mathrm{A}}=1.5 \mathrm{V}\end{array}$

Also, between B and C

${\mathrm{V}}_{\mathrm{B}}-1\times 2.5+2={\mathrm{V}}_{\mathrm{C}}$

$\Rightarrow {\mathrm{V}}_{\mathrm{C}}=-0.5 \mathrm{V}$