(i) 4-Nitropropiophenone

Here, Ketone group is the functional group in this compound and a nitro group is attached at a 4^th position with respect to the ketone group. Therefore, the structure of this compound is given below;

(ii) 2-Hydroxycyclopentanecarbaldehyde

Here, aldehyde and a ketone group are the functional group in this compound and the hydroxyl group is attached at the 2^nd position with respect to the aldehyde group. Therefore, the structure of this compound is given below;

(iii) Phenyl acetaldehyde

Here, aldehyde group is the functional group in this compound and acetaldehyde group is attached to a phenyl ring. Therefore, the structure of this compound is given below;