$[Co_2(CO)_8]$ displays

Which of the following organometallic compounds possesses both $\sigma$ and $\pi$ bonds?

Which of the following are organometallic compounds? $(I)$ Grignard reagent $(II)$ Trimethylboron $(III)$ Sodium methoxide $(IV)$ $TEL$

In $Fe(CO)_5$,the $Fe-C$ bond possesses

The correct statement$(s)$ regarding the binary transition metal carbonyl compounds is (are) (Atomic numbers: $Fe = 26, Ni = 28$)
$A$. Total number of valence shell electrons at metal centre in $Fe(CO)_5$ or $Ni(CO)_4$ is $16$
$B$. These are predominantly low spin in nature
$C$. Metal-carbon bond strengthens when the oxidation state of the metal is lowered
$D$. The carbonyl $C-O$ bond weakens when the oxidation state of the metal is increased

Which of the following is incorrect for the complex $[Fe(CO)_x]$?