Paramagnetic properties are due to the realignment of the electron path caused by the external magnetic field. Paramagnetic nature ∝ number of unpaired electron
Metal ion
d-electron
Number of unpaired e−
Cu2+
↿⇂
↿⇂
↿⇂
↿
↿
2
V2+
↿
↿
↿
3
Cr2+
↿
↿
↿
↿
4
Mn2+
↿
↿
↿
↿
↿
5
So increasing order of paramagnetic nature Cu2+<V2+<Cr2+<Mn2+ Hence, the correct option is (a).