Among the given complexes the possess " $\mathrm{CO}^{\prime \prime}$ as a bridged ligands are

I. $\left[\mathrm{Co}_2(\mathrm{CO})_8\right]$

II. $\left[\mathrm{Fe}_3(\mathrm{CO})_{12}\right]$

III. $\left[\mathrm{Mn}_2(\mathrm{CO})_{10}\right]$

IV. $\left[\mathrm{Fe}_2(\mathrm{CO})_9\right]$

The correct order of decreasing field strength of the below given ligands is

When $\left[\mathrm{Ti}\left(\mathrm{H}_2 \mathrm{O}\right)_6\right] \mathrm{Cl}_3$ is heated at $250^{\circ} \mathrm{C}$, the change in colour is from

Which compound is zero valent metal complex?