A student studied how substrate concentration affects the rate of an enzyme-catalysed reaction. The student displayed the results on a graph. What is the $K_m$ for this enzyme-catalysed reaction?
- A$12\ \text{mol dm}^{-3}$
- B$15\ \text{mol dm}^{-3}\ \text{s}^{-1}$
- C$30\ \text{mol dm}^{-3}\ \text{s}^{-1}$
- D$50\ \text{mol dm}^{-3}$