Since the structures are not given, I'll just provide the structure for these functional groups.
Alkane: You know the compound is an alkane if it conforms to the general formula CₓH₂ₓ₊₂, where x is any positive integer.
Alcohol: A compound is an alcohol if the compound contains an -OH functional group.
Carboxylic acid: The general formula for carboxylic acid is RC=OOH. The R is any hydrocarbon chain. The C atom is attached to one oxygen atom by a double bond, and one O atom by a single bond.