A liquid was mixed with ethanol and a drop of concentrated ${\text{H}}_2{\text{SO}}_4$ was added. A compound with a fruity smell was formed. The liquid was:

1. A
   ${\text{CH}}_3\text{OH}$
2. B
   $\text{HCHO}$
3. C
   ${\text{CH}}_3{\text{COCH}}_3$
4. D
   ${\text{CH}}_3\text{COOH}$