The compound that does not answer iodoform test is

The iodoform test is given by compounds containing a \(CH_3-CO-\) group (methyl ketones and acetaldehyde) or a \(CH_3-CH(OH)-\) group (which can be oxidized to a methyl ketone).

Ethanal (\(CH_3CHO\)) contains a \(CH_3-CO-\) group, hence it gives the iodoform test.

Acetone (\(CH_3COCH_3\)) contains a \(CH_3-CO-\) group, hence it gives the iodoform test.

Acetophenone (\(C_6H_5COCH_3\)) contains a \(CH_3-CO-\) group, hence it gives the iodoform test.

Ethanoic acid (\(CH_3COOH\)) is a carboxylic acid. In the presence of the basic reagent (\(NaOH + I_2\)), it undergoes an acid-base reaction to form the acetate ion (\(CH_3COO^-\)), which does not undergo the haloform reaction. Thus, it does not give the iodoform test.

Answer: Ethanoic acid