The correct option is A n-Butyl alcohol
Iodoform test is used to check the presence of carbonyl compounds with the structure R−CO−CH3 or alcohols with the structure R−CH(OH)−CH3 in a given unknown substance.
When Iodine and sodium hydroxide are added to a compound that contains either a methyl ketone or a secondary alcohol with a methyl group in the alpha position, a pale yellow precipitate of iodoform or triiodomethane is formed. It can be used to identify aldehydes or ketones. If an aldehyde gives a positive iodoform test, then it must be acetaldehyde since it is the only aldehyde with a CH3C=O group.
For haloform reaction, 3 hydrogens on alpha carbon are required. As option (a) is a primary alcohol and it does not have any alpha H, it will not give positive iodoform test. Hence, the correct answer is option (a).