c
Spin only magnetic moment depends upon the number of unpaired electrons.

Magnetic moment, \(\mu=\sqrt{n(n+2)}\)

Where, \(n=\) number of unpaired electrons

The electronic configuration for the given ions is as follow:

For \(M n^{2+}[Z=25]=1 s^{2}, 2 s^{2}, 2 p^{6}, 3 s^{2} 3 p^{6}, 3 d^{2} 4 s^{0}\)

\(\mathop {\boxed \uparrow \boxed \uparrow \boxed \uparrow \boxed \uparrow \boxed \uparrow }\limits^{3{d^2}} \)

\(\mu=\sqrt{5(5+2)}=\sqrt{35}\)

For \(C r^{2+}[Z=24]=1 s^{2}, 2 s^{2} 2 p^{6}, 3 s^{2} 3 p^{6}, 3 d^{4}, 4 s^{0}\)

\(\mathop {\boxed \uparrow \boxed \uparrow \boxed \uparrow \boxed \uparrow }\limits^{3{d^4}} \)

\(\mu=\sqrt{4(4+2)}=\sqrt{24}\)

For \(T i^{2+}[Z=22]=1 s^{2}, 2 s^{2} 2 p^{6}, 3 s^{2} 3 p^{6}, 3 d^{2}, 4 s^{0}\)

\(\mathop {\boxed \uparrow \boxed \uparrow \boxed \uparrow }\limits^{3{d^2}} \)

\(\mu=\sqrt{2(2+2)}=\sqrt{8}\)

\(\therefore\) correct order of spin only magnetic moment is

\(M n^{2}+C r^{2+}>T i^{2+}\)