A compound (A) with molecular formula $\text{C}_4\text{H}_9\text{I}$ which is a primary alkyl halide, reacts with alcoholic $\text{KOH}$ to give compound (B). Compound (B) reacts with $\text{HI}$ to give (C) which is an isomer of (A). When (A) reacts with $\text{Na}$ metal in the presence of dry ether, it gives a compound (D), $\text{C}_8\text{H}_{18}$, which is different from the compound formed when n-butyl iodide reacts with sodium. Write the structures of (A), (B), (C) and (D). Write the chemical equation when compound (A) is reacted with alcoholic $\text{KOH}$.