Which of the following statements is true about the worm phyla? Annelida, Platyhelminthes, and Nematoda all have animals with a coelom
many annelids are parasites, but flatworms and roundworms help fertilize the soil
Annelida and Nematoda phyla are the simplest of all worms while Platyhelminthes are complex worms
most annelids are free-living animals, but most flatworms and roundworms are parasites

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.