The table shows the results when four different solutions, A, B, C, and D, are tested with universal indicator and a pH probe:
| Solution | Colour when universal indicator is added | Reading on pH probe |
|---|---|---|
| A | purple | 13 |
| B | green | 7 |
| C | orange | 5 |
| D | red | 2 |
Which of these solutions is a weak acid?
A
B
C
D