Multiple choice general knowledge science & technology Which of these contains the carbonyl group? Ketones Aldehydes Esters All of the above Reveal answer Fill a bubble to check yourself D Correct answer Explanation The carbonyl group (C=O) is present in all three compound types: ketones (RCOR'), aldehydes (RCHO), and esters (RCOOR'). Each contains a carbon-oxygen double bond as a defining functional group.