Provide your best answer for the following question. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The question is: Several types of mechanisms in the body regulate the rate of chemical reactions in the digestive system. Among the most important are feedback systems, which control the release rate of
enzymes.
digestive enzymes, hydrochloric acid, and bile.