The graph illustrates the activity of three digestive enzymes at different pH values. Which statement is correct?
- AEnzymes X and Y are both active at $\text{pH }7$.
- BEnzymes X and Z are both active at $\text{pH }4$.
- CEnzymes Y and Z are both active at $\text{pH }4$.
- DEnzymes Y and Z are both active at $\text{pH }8$.