(A)

Complexes in which a metal is bound to only one kind of donor groups are known as homoleptic. Complexes in which a metal is bound to more than one kind of donor groups are known as heteroleptic. (1) is homoleptic. (2), (3) and (4) are heteroleptic.

(A)

Multiplicity of simple ligands is denoted by di, tri, tetra etc. and multiplicity of complex ligands is denoted by bis, tris, tetrakis etc.

$[\stackrel{+2}{\mathrm{Pt}} \stackrel{-1}{{\mathrm{Br}}_2 }{\left({\stackrel{0}{\mathrm{PMe}}}_3\right)}_2]$ : dibromobis (trimethylphosphine) platinum(II)

(A)

Since both N and P have lone pair of electrons in $\mathrm{N}{\left({\mathrm{CH}}_3\right)}_3$ and $\mathrm{P}{\left({\mathrm{CH}}_3\right)}_3$, these act as ligands and form complexes. P has vacant d orbital hence $\mathrm{P}{\left({\mathrm{CH}}_3\right)}_3$ act as $\mathrm{\pi }$ acceptor ligand, but $\mathrm{N}{\left({\mathrm{CH}}_3\right)}_3$ cannot do so as N does not have a vacant d orbital.