Which of the following compounds does not exhibit paramagnetism?

$A$ metal complex of coordination number six having three different types of ligands $a$,$b$ and $c$ of composition $Ma_2b_2c_2$ can exist in several geometrical isomeric forms; the total number of such isomers is

Which of the following complexes does not show optical isomerism?

The magnetic moment of the central metal ion in $K_2MnO_4$ is ........ $B.M.$

Which of the following is expected to be a paramagnetic complex?

Which of the following ions has the lowest magnetic moment?