Chemical mechanisms that can turn off or reduce an enzyme are . a.) inhibitors
b.) activators
c.) centrioles
d.) vacuoles

Explanation:

Chemical mechanisms that can turn off or reduce an enzyme are inhibitors. Explanation; -Enzyme inhibitors are molecules or compounds that bind to enzymes and result in a decrease in their activity. They can bind to an enzyme and stop a substrate from entering the enzyme's active site and/or prevent the enzyme from catalyzing a chemical reaction.

halogen, any of the six nonmetallic elements that constitute group 17 (group viia) of the periodic table. the halogen elements are fluorine (f), chlorine (cl), bromine (br), iodine (i), astatine (at), and tennessine (ts).

stress fractures occur largely in the feet and legs and are common in sports that require repetitive impact, primarily running/jumping sports such as gymnastics or track and field.