Which of the following $$3\mathrm{d}$$-metal ion will give the lowest enthalpy of hydration $$\left(\Delta_{\text {hyd }} \mathrm{H}\right)$$ when dissolved in water ?

Octahedral complexes of copper(II) undergo structural distortion (Jahn-Teller). Which one of the given copper (II) complexes will show the maximum structural distortion? (en - ethylenediamine; $$\mathrm{H}_{2} \mathrm{~N}_{-} \mathrm{CH}_{2}-\mathrm{CH}_{2}-\mathrm{NH}_{2}$$)

Correct structure of $$\gamma$$-methylcyclohexane carbaldehyde is

Compound 'A' undergoes following sequence of reactions to give compound 'B'.

The correct structure and chirality of compound 'B' is

[where Et is $$\left.-\mathrm{C}_{2} \mathrm{H}_{5}\right]$$