Concept:
Denticity is the number of donor atoms through which a ligand attaches to central metal ion.
Step 1:
Pyridine donates through one nitrogen atom.
\[
A \rightarrow IV
\]
Step 2:
DMG acts as bidentate ligand.
\[
B \rightarrow III
\]
Step 3:
EDTA is hexadentate ligand.
\[
C \rightarrow II
\]
Dien is tridentate ligand.
\[
D \rightarrow I
\]
Step 4:
Final matching:
\[
A-IV,\quad B-III,\quad C-II,\quad D-I
\]
\[
\boxed{\text{Correct Option = (3)}}
\]