Right choice is (c) 7.5V
The best I can explain: Taking the mesh currents in the three meshes as I1, I2 and I3, the mesh equations are:
3I1+0I2+0V=5
-2I1-4I2+0V=0
0I1+9I2+V=0
Solving these equations simultaneously and taking the value of I2=0, we get V=7.5V.