Which $d-$orbital of metal in $[Fe(CO)_5]$ is involved in hybridisation?

Which of the following systems in an octahedral complex has the maximum number of unpaired electrons?

When $(n-1)d$ orbitals participate in the hybridization of a coordination complex,the resulting complex is known as:

The hybridization of $Ag^+$ in the linear complex $[Ag(NH_3)_2]^+$ is

$NiCl_2\{P(C_2H_5)_2(C_6H_5)\}_2$ exhibits temperature-dependent magnetic behaviour (paramagnetic/diamagnetic). The coordination geometries of $Ni^{2+}$ in the paramagnetic and diamagnetic states are respectively

The complex $[Ag(NH_3)_2]^{+}$ has $sp$ hybridization and is a ...... complex.