Correct IUPAC name of is:

pent-2-enal pent-2-enol pent-3-enal pent-3-enol

pent-2-enal

The parent chain has 5 carbon atoms and one of them is an aldehyde group so numbering starts from there. There is a double bond on the 2nd carbon atom. So, the name of the compound will be pent-2-enal