Why does contact with animals increase the risk of influenza infection? a. increased population density occurs with animal contact. b. influenza can also infect and be carried by animal species. c. interaction with animals can decrease the vaccine's effect. d. animal contact decreases immune system responsiveness.

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.