Blocks of agar are coloured with a pH indicator and then used to explore the diffusion of an acid solution. Which block would undergo a complete colour change most quickly?
- A$1\text{ mm} \times 1\text{ mm} \times 1\text{ mm}$
- B$1\text{ mm} \times 0.25\text{ mm} \times 0.25\text{ mm}$
- C$1\text{ mm} \times 0.5\text{ mm} \times 0.5\text{ mm}$
- D$2\text{ mm} \times 0.5\text{ mm} \times 0.5\text{ mm}$