If the ___________ firm has zero costs or only has fixed cost, the quantity supplied in equilibrium is given by the point where the average revenue is zero.
In animals like Annelids, Molluscs, organs have associated to form functional systems, each system concerned with a specific physiological function. This pattern is called ________ system level of organization.
Based on the common features like presence of notochord and dorsal hollow neural system, animals like fishes, amphibians, reptiles, birds along with mammals are included in which Phylum?