(i) HCHO (ii) CH3CHO (iii) CH3CH2CHO (iv) CH3CH2CH2CHO
(ii) The IUPAC name of CH3CHO is Ethanal.
(iii) The IUPAC name of CH3CH2CHO is Propanal.
(iv) The IUPAC name of CH3CH2CH2CHO Butanal.