Answer
IUPAC: 3-phenylbutanal
Common name: β-phenylbutyraldehyde
Work Step by Step
IUPAC: There are 4 carbons and its an aldehyde so its butanal. And since there is a phenyl group on the third carbon, its 3-phenylbutanal.
Common name: The carbon attached to the C=O bond is alpha carbon and the next carbon is beta. There are four carbons on the left side of the C=O, its butyraldehyde. And since the phenyl is attached to the beta carbon its β-phenylbutyraldehyde