Question

ph at which an enzyme works best
optimal ph
lock & key
active site
specific

Explanation:

To determine the term related to the pH at which an enzyme works best, we analyze each option:

• Optimal pH: By definition, the optimal pH of an enzyme is the specific pH value at which the enzyme exhibits its maximum activity (works best).
• Lock & Key: This refers to the enzyme - substrate binding model, not directly related to the pH for optimal enzyme function.
• Active Site: It is the region of an enzyme where the substrate binds, and it is not about the pH at which the enzyme works best.
• Specific: This is a general term about enzyme - substrate specificity, not related to the pH for optimal activity.

Answer:

Optimal pH