An organic compound A upon reacting with ${\text{NH}}_3$ gives B. On heating B gives C. C in presence of $\text{KOH}$ reacts with ${\text{Br}}_2$ to give ${\text{CH}}_3{\text{CH}}_2{\text{NH}}_2$. A is:

1. A
   ${\text{CH}}_3{\text{CH}}_2{\text{CH}}_2\text{COOH}$
2. B
   ${\text{CH}}_3{\text{CH(CH}}_3)\text{COOH}$
3. C
   ${\text{CH}}_3{\text{CH}}_2\text{COOH}$
4. D
   ${\text{CH}}_3\text{COOH}$