Concept:Alkanals are more commonly called aldehydes.Their functional group is attached to the end of a carbon chain.Explanation:The general formula for an alkanal is RCHO.This means the carbonyl carbon is bonded to at least one hydrogen atom.The R group may be a hydrogen atom, an alkyl group, or an aryl group.Alkanones (ketones) fit R2CO, alcohols fit ROH, and esters fit RCOOR.Only the alkanals have the −CHO terminal group.Answer:B. RCHO