${\mathrm{LiAlH}}_4$ is a reducing agent and reduces carboxylic acid to alcohol. 

${\text{CH}}_{3}COOH\stackrel{{\text{LiAlH}}_4}{\to }{\text{CH}}_3-{\text{CH}}_2-\text{OH}$
                                                   (A)

$\stackrel{{\text{PCl}}_5}{\to }{\text{CH}}_3-{\text{CH}}_2-\text{Cl}\underset{\text{KOH}}{\overset{\text{alc}}{\to }}{\text{ CH}}_2={\text{CH}}_2$