Cationic complex is

A cationic complex is one in which the complex ion has a net positive charge.

Cuprammonium salt is [Cu(NH₃)₄]SO₄.

Cationic complexes, for example. $\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]{\mathrm{Cl}}_3,\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3,{\left[\mathrm{Ni}{\left({\mathrm{NH}}_3\right)}_6\right]}_2{\mathrm{Cl}}_2$This is evident from the reactions listed below.

$\begin{array}{l}\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_3\rightleftharpoons {\left[\mathrm{Co}{\left({\mathrm{NH}}_3\right)}_6\right]}^{3+}+3{\mathrm{Cl}}^{-}\\ \left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]{\mathrm{Cl}}_3\rightleftharpoons {\left[\mathrm{Fe}{\left({\mathrm{H}}_2\mathrm{O}\right)}_6\right]}^{3+}+3{\mathrm{Cl}}^{-}\\ \left[\mathrm{Ni}{\left({\mathrm{NH}}_3\right)}_6\right]{\mathrm{Cl}}_2\rightleftharpoons {\left[\mathrm{Ni}\left({\mathrm{NH}}_3\right)6\right]}^{2+}+2{\mathrm{Cl}}^{-}\end{array}$

Therefore, the correct option is (C) Cuprammonium (II) sulphate.