Number of complexes from the following with even number of unpaired "$d$" electrons is . . . . . . . . . .
${\left[\mathrm{V}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+}, \quad\left[\mathrm{Cr}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}, \quad\left[\mathrm{Fe}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+},}$
${\left[\mathrm{Ni}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{3+},\left[\mathrm{Cu}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right]^{2+}}$
[Given atomic numbers: $\mathrm{V}=23, \mathrm{Cr}=24, \mathrm{Fe}=26$,
$\mathrm{Ni}=28, \mathrm{Cu}=29]$