DHA is a colourless liquid that reacts with protein in the skin, making it darken. Its structure is shown below. $\text{HOCH}_2\text{COCH}_2\text{OH}$ What observations would be seen during tests on this substance?
- A1, 2 and 3
- B1 and 2 only
- C2 and 3 only
- D1 only