An example for –COOR functional group is

Ester functional group is 

A) ${\text{CH}}_{\text{3}}{\text{COOC}}_{\text{2}}{\text{H}}_{\text{5}}\Rightarrow {\text{CH}}_{\text{3}}{\text{COOCH}}_{\text{2}}{\text{CH}}_3$  ethyl acetate 

B) ) Propane amine  ${\text{CH}}_{\text{3}}{\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{NH}}_2$

C) ${\text{CH}}_{\text{3}}\text{CHO}$ - Acetaldehyde (or) Ethanol

D) ${\text{CH}}_3\text{COOH}$ - Acetic acid (or) ethanoic acid.