Explanation

(b)
(i) In nucleophilic substitution reaction more powerful nucleophile replaces weaker nucleophile.
(ii) In rearrangement reaction atoms replace their position within molecule.
(iii) In elimination reaction small molecules $(e.g.,\ H_{2}O,\ NH_{3})$ are lost.
$R - CH_{2}CH_{2}Cl + KOH\ (alc.)\overset{\ \ \ \ \ \ \ \mathrm{\Delta}\ \ \ \ \ }{\rightarrow}RCH = CH_{2} + KCl + H_{2}O$
$\because KCl\ and\ H_{2}O$molecules are lost during reaction.
$\therefore$ It is an elimination reaction.