Which one of the following gives a negative Tollens' test but a positive iodoform test?

(a) Product of hydrolysis ${\mathrm{HCOOC}}_3{\mathrm{H}}_5$

(b) Product of ${\mathrm{CH}}_3-\stackrel{\underset{\left|\right|}{\mathrm{O}}}{\mathrm{C}}-{\mathrm{CH}}_2-\mathrm{COOH}$ on heating

(c) Product of hydrolysis of ${\mathrm{CH}}_3\mathrm{COCH}\left({\mathrm{OCH}}_3\right){\mathrm{CH}}_3$