A reversible inhibitor that only affects multi substrate enzymes and binds to the enzyme only after one substrate has bound is a(n) ___

Uncompetitive inhibitor.

Explanation:  

Enzymes are the biological catalysts that catalyze the biological process and metabolic activity of the body. Without enzymes, all the biological activity becomes very slow. Enzyme provides suitable speed for the biological process. All enzymes are made up of protein. The uncompetitive inhibitor is the type of enzyme that only disturbs or affects multi-substrate enzymes and joins to enzymes only after one substrate has bound.  

b. the carbon cycle ensures living things have a source of hydrogen