If $\text{HOCH}_2\text{CHO}$ is heated under reflux with an excess of acidified $\text{K}_2\text{Cr}_2\text{O}_7$ until no further change occurs, what final product is formed in this reaction?
- AHOOCCHO
- B$\text{HOCH}_2\text{COOH}$
- CHOOCCOOH
- D$\text{HOOCCH}_2\text{COOH}$