The correct increasing order of trans-effect of the following species is:

1.  ${\mathrm{NH}}_3>{\mathrm{CN}}^{-}>\mathrm{Br}>{\mathrm{C}}_6{\mathrm{H}}_5^{-}$

2.  ${\mathrm{CN}}^{-}>{\mathrm{C}}_6{\mathrm{H}}_5^{-}>{\mathrm{Br}}^{-}>{\mathrm{NH}}_3$

3.  ${\mathrm{Br}}^{-}>{\mathrm{CN}}^{-}>{\mathrm{NH}}_3>{\mathrm{C}}_6{{\mathrm{H}}^{-}}_5$

4.  ${\mathrm{CN}}^{-}>{\mathrm{Br}}^{-}>{\mathrm{C}}_6{{\mathrm{H}}^{-}}_5>{\mathrm{NH}}_3$

The correct statement among the following regarding [Mn(CN)₆]^3-is:

1. It is sp³d² hybridized and tetrahedral.

2. It is d²sp³ hybridized and octahedral.

3. It is dsp² hybridised and square planar.

4. It is sp³d² hybridised and octahedral.

Iron carbonyl, $\mathrm{Fe}{\left(\mathrm{CO}\right)}_5$, is classified as:

The number of possible isomers for the complex \([Co (en)_ 2 Cl_ 2] 𝐶 𝑙  \) will be:
(en=ethylenediamine)