During the course of estimating nitrogen using Kjeldahl's method, the organic compound is heated with

An organic compound, ' $A$ ' with molecular formula $\mathrm{C}_8 \mathrm{H}_8 \mathrm{O}$ on reaction with $\mathrm{I}_2 / \mathrm{KOH}$ gives salt of carboxylic acid ' $B$ ' and a halo-compound ' $C$ '. Compound ' $C$ ' on the reaction with silver powder gives ' $D$ '. The structures of ${ }^{\prime} A^{\prime}$ and ' $D^{\prime}$ are

The order of circled $\mathrm{C}-\mathrm{H}$ bond dissociation energy in the following compound is

Intercepts of a plane in crystal is given by $a, b / 2,3 c$ in a simple cubic unit cell. The miller indices are