Which of the following statement is correct with respect to the metal carbonyl of $\mathrm{Ist}$ transition series?

AS $\mathrm{M}-$carbonating increases $\mathrm{C}-\mathrm{O}$ bond length and decreases bond order by three to two and half. 
$\mathrm{Bond} \mathrm{order} = \frac{1}{\mathrm{Bond} \mathrm{length} }$
As the positive charge on the central one tar atom increases, so does the bend length. As the electron density on the opposite metal arm increases, so does the bend length.
The correct answer is D.