The 18-valence electron rule asserts that transition metal compounds are thermodynamically stable when they have a total of 18 valence electrons on the central metal, which include the metal$$'$$s d electrons and the electrons provided by the ligands attached to the metal. The 18-electron rule is obeyed by

A

$$[\text{Fe(CO)}_5]$$

B

$$[\text{Mn(CO)}_5]$$

C

$$[\text{Ni(CO)}_4]$$

D

$$[\text{Cr(CO)}_6]$$