Head, Foot and Visceral mass- this combination of characters is diagnostic feature ofA Echinoderms B Arthropods C Mollusca D Annelida

To answer the question, we need to identify the group of animals that possess the combination of head, foot, and visceral mass as a diagnostic feature.

A. Echinoderms: Echinoderms, such as starfish and sea urchins, do not have a distinct head or foot. They have a central body region called the central disc, from which their arms or spines radiate. Therefore, echinoderms do not possess the combination of head, foot, and visceral mass.

B. Arthropods: Arthropods, including insects, spiders, and crustaceans, have a distinct head and foot. However, they do not possess a visceral mass. Instead, their internal organs are divided into segments throughout their body. Therefore, arthropods do not possess the combination of head, foot, and visceral mass.

C. Mollusca: Mollusks, such as snails, clams, and octopuses, have a distinct head, foot, and visceral mass. The head contains sensory organs, the foot is used for locomotion, and the visceral mass houses the internal organs. Therefore, mollusks possess the combination of head, foot, and visceral mass.

D. Annelida: Annelids, including earthworms and leeches, have a distinct head and a segmented body with a well-developed coelom (body cavity). However, they do not possess a distinct foot. Instead, they use their entire body for locomotion. Therefore, annelids do not possess the combination of head, foot, and visceral mass.

Based on the information provided, the group of animals that possess the combination of head, foot, and visceral mass as a diagnostic feature is C. Mollusca.