The indicator cresol red turns from red to yellow when placed in an acid. Several agar blocks containing cresol red were cut into different sizes and then placed in an acid. Every other variable was kept the same. The blocks were measured in $\text{mm}$. Which block turned completely yellow the fastest?
- A$3 \times 30 \times 30$
- B$6 \times 6 \times 6$
- C$6 \times 12 \times 12$
- D$12 \times 12 \times 12$