The compound which does not respond to iodoform test is

Iodoform test is given compounds have either ${\mathrm{CH}}_3-\mathrm{CO}-$ group or ${\mathrm{CH}}_3-\mathrm{CHOH}-$ group.

The reagents of the iodoform test:

$$\begin{gathered} \left(1\right) {\mathrm{I}}_2+\mathrm{NaOH} \\ \left(2\right) {\mathrm{I}}_2+{\mathrm{OH}}^{-} \\ \left(3\right) \mathrm{NaOI} \end{gathered}$$

Thus, ${\mathrm{CH}}_3-\mathrm{CHO}$, ${\mathrm{CH}}_3-\mathrm{CH}\left(\mathrm{OH}\right)-{\mathrm{CH}}_3$ and ${\mathrm{C}}_6{\mathrm{H}}_5{\mathrm{COCH}}_3$ give positive iodoform when warmed with ${\mathrm{I}}_2+\mathrm{NaOH}$ and ${\mathrm{C}}_2{\mathrm{H}}_5-\mathrm{CO}-{\mathrm{C}}_2{\mathrm{H}}_5$ does not respond to the iodoform test.