Species having the same number of unpaired electrons, have same magnetic moment.
(a) $MnCl _{2} \Rightarrow Mn ^{2+}=[ Ar ] 3 d^{5}, 4 s^{0}$
(five unpaired electrons)
$CuSO _{4} \Rightarrow Cu ^{2+}=[ Ar ] 3 d^{\frac{1}{9}}, 4 s^{0}$
(one unpaired electron)
(b) $CuCl _{2} \Rightarrow Cu ^{2+}=[ Ar ] 3 d^{9}, 4 s^{0}$
(one unpaired electron)
$TiCl _{3} \Rightarrow Ti ^{3+}=[ Ar ] 3 d^{1}, 4 s$
(one unpaired electron)
$\therefore CuCl _{2}$ and $TiCl _{3}$ have same magnetic moment.
$\mu=\sqrt{1(1+2)}=\sqrt{3}=1.73 BM$
(c) $TiO _{2} \Rightarrow Ti ^{4+}=[ Ar ] 3 d^{0}, 4 s^{0}$
(no unpaired electron)
$CuSO _{4} \Rightarrow Cu ^{2+}=[ Ar ] 3 d^{9}, 4 s^{0}$
(one unpaired electron)
(d) $TiCl _{3} \Rightarrow Ti ^{3+}=[ Ar ] 3 d^{1}, 4 s^{0}$
(one unpaired electron)
$NiCl _{2} \Rightarrow Ni ^{2+}=[ Ar ] 3 d^{8}, 4 s^{0}$
(two unpaired electrons)