Inhibition of succinate dehydrogenase by malonate is an example of:
A.Non competitive inhibition
B.Competitive inhibition
C.Allosteric inhibition
D.Negative feedback

Hint: Malonate is a competitive inhibitor of the enzyme succinate dehydrogenase: malonate binds to the active sites of the enzyme without reacting, and so competes with succinate, the usual substrate of the enzyme.

Complete answer:
Noncompetitive inhibition is a type of enzyme inhibition where the inhibitor reduces the activity of the enzyme and binds equally well to the enzyme whether or not it has already bound to the substrate. The inhibitor may bind to the enzyme whether or not the substrate has already been bound, but if it has a higher affinity for the binding of enzyme in one state or the other it is called a mixed inhibitor. Competitive inhibition is interruption of a chemical pathway owing to one chemical substance inhibiting the effect of another by competing with it for binding or bonding. Whereas allosteric regulation or allosteric control is the regulation of an enzyme by binding an effector molecule at a site other than enzymes active site decides to which the effector binds is termed as allosteric site to regulatory site. Effectors that enhance the proteins activity are referred to as allosteric activators, whereas those that decrease the proteins activity are known as allosteric inhibitors. Allosteric regulations are a natural example of control systems, such as feedback from downstream products or feed forward from upstream substrates. Allosteric regulation is also particularly important in the cells ability to adjust enzyme activity. The enzyme succinate dehydrogenase is a classic example of competitive inhibition with succinic acid as its substrate. The compound namely, malonic acid, glutaric acid and oxalic, have structural similarity with succinic acid and compete with the substrate for binding at the active sites of the succinate dehydrogenase enzyme.

Hence the correct answer is option(B)

Note: Allosteric sites allow effectors to bind to the protein, often resulting in conformational changes involving protein dynamics.