Following figures show the arrangement of bar magnets in different configurations. Each magnet has magnetic dipole moment $\overrightarrow{\mathrm{m}}$ . Which configuration has highest net magnetic dipole moment?

Net dipole moment is given by ${\overrightarrow{m}}_1+{\overrightarrow{m}}_2$

Magnitude of ${\overrightarrow{m}}_1+{\overrightarrow{m}}_2$ is $\sqrt{{m_1}^2+{m_2}^2+2m_1{m}_2\cos \theta }$.

The resultant value is maximum for the configuration with minimum angle between them. Therefore configuration C will have maximum net dipole moment.