Which of the following species acts as strongest oxidising agent?

Identify isoelectronic pair from following.

When 0.01 mole of nonvolatile solute is dissolved in certain solvent calculate the mass of solvent in kg if $\Delta \mathrm{T}_{\mathrm{b}}=0.6 \mathrm{~K}$ and $\mathrm{K}_{\mathrm{b}}$ for solvent= $2 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$

Which from following polymers contains $-\mathrm{CO}-\mathrm{NH}-$ linkage?