The enzyme β-galactosidase is able to catalyse the hydrolysis of four substrates, A, B, C and D, which have similar structures. Each substrate has a different $K_m$ value. Which substrate does β-galactosidase have the lowest affinity for?
- A$K_m = 4 \times 10^{-3}\ \text{mol dm}^{-3}$
- B$K_m = 1 \times 10^{-3}\ \text{mol dm}^{-3}$
- C$K_m = 2 \times 10^{-4}\ \text{mol dm}^{-3}$
- D$K_m = 1 \times 10^{-4}\ \text{mol dm}^{-3}$