The correct choice is (b) Mechanism of allosteric enzymes by modulators
For explanation: In the above diagram, mechanism for inhibition and stimulation by modulators of allosteric enzyme is shown. When negative modulators are involved the substrate is removed from the catalytic site, hence no ES complex formed, hence no product. During the use of positive modulators, the positive modulator attaches to its allosteric site and encourages more substrate to bind to the catalytic site forming ES complex and hence more product is formed.