Correct Answer - A
`Fe^(2+)(Z=26)3d^(6)`, one electron unpaired electron
`Zn^(0)(Z=30)4s^(2)3d^(10),"No unpaired electron"`
`Hg^(2+)(Z=80)6d^(10),"No unpaired electron"`
`Ti^(4+)(Z=22)[Ar]^(18),"No unpaired electron"`
Only `Fe^(2+)` is paramagnetic in nature.