Answer:
Step-by-step explanation:
An enzyme is a protein that speeds up a chemical reaction. Enzymes are shape specific. The active site is a specific shape, which means it can only break down specific substrates.
Certain conditions can denature enzymes. For example, extreme temperatures or pH will cause the enzyme to deform and change shape, which means it cannot perform its job.
Therefore, the best choice is the second one: enzymes work best in specific conditions and only break down specific substrates.