Which functional group is found in an ester?

The functional group found in an ester is a carbonyl group with an attached second oxygen atom that is bonded to a carbonyl carbon substituent by a single bond, usually a pair of alkyl or aromatic groups. In addition, it can be shown in text as RCOOR or occasionally as ROCOR, which made them responsible in the distinctive and attractive odors and flavors of many flowers, perfumes, and ripe fruits.  

it’s previous models   because when i picked that son of a gun’s answer it was wrong look for previous models because they might make it a different letter