Which of the following statements about enzymes are true? choose all that apply a.) an enzyme yields a specific product, whereas a nonbiologival catalyst may produce more than one product, and side reactions may occur. b.) generally, an enzyme is specific for a substrate. for example, thrombin catalyzes the hydrolysis of the peptide bond between arg and gly. c.) a substrate must bind to the active site before a reaction occurs. d.) reactions occur at the active site, which usually consists of a crevice on the surface of the enzyme e.) nonbiological catalysts and enzymes tend to have a similar degree of reaction specificity.