A student was given two test-tubes: one contained $10\,\text{cm}^3$ of solution P and the other contained $10\,\text{cm}^3$ of solution Q. After the solutions were mixed and left standing for $24$ hours, the concentration of P fell, but the concentration of Q did not change. The student then recorded the following conclusions. 1. P may decompose over time. 2. Q may function as a biological catalyst. 3. P may act as the substrate for Q. Which conclusions could be supported by the evidence?
- A1, 2 and 3
- B1 and 2 only
- C1 only
- D2 and 3 only