Some reactions of NO$$_2$$ relevant to photochemical smog formation are

Identify A, B, X and Y :

The variation of the rate of an enzyme catalyzed reaction with substrate concentration is correctly represented by graph :

'25 volume' hydrogen peroxide means

The radius of the $$\mathrm{2^{nd}}$$ orbit of $$\mathrm{Li^{2+}}$$ is $$x$$. The expected radius of the $$\mathrm{3^{rd}}$$ orbit of $$\mathrm{Be^{3+}}$$ is