Question

enzymes and substrates fit together based on their specific shapes like a key fits a lock
optimal ph
denature
base (alkaline)
lock and key model

Explanation:

The statement describes how enzymes and substrates interact based on their specific shapes, which is the core concept of the Lock and Key Model. The other options: "Optimal pH" relates to enzyme activity conditions, "Denature" is about enzyme structure change, and "Base (alkaline)" is a type of pH environment, none match the described interaction mechanism.

Answer:

Lock and Key Model