Question

Largest living invertebrates belongs to the phylum
A.Arthropoda
B.Annelida
C.Mollusca
D.Echinodermata

Answer 1

Hint: The largest living invertebrate belongs to the phylum Mollusca. Molluscs are triploblastic, bilaterally symmetrical coelomate organisms with organ system level of organization. Few organisms undergo torsion.

Complete answer:The largest living invertebrate is Architeuthis or Giant Atlantic Squid. It is the largest (55 feet) and heaviest (8 tonnes) invertebrate. They have the largest eyes. They belong to the phylum Mollusca.
Mollusca is the second-largest animal phylum. Molluscs are triploblastic, coelomate (schizocoelic) organisms with organ system level of organization. They have bilateral symmetry, but some are asymmetrical due to torsion as they grow.
The body is soft and unsegmented, divisible into the head with sensory tentacles, foot, and visceral hump (contain digestive tract and other visceral organs). The soft body is covered by a fleshy fold called mantle/pallium. The mantle cavity is present between the visceral hump and mantle.
In Mollusca, respiration is carried out by feather-like gills(ctenidia) in the mantle cavity or pulmonary chamber. Gills also help in excretion. The digestive system is well developed. It contains a rasping organ called radula for feeding. The excretory organ is one or two pairs of kidneys. The nervous system consists of paired ganglia. They are dioecious and oviparous with indirect development.
So, the correct answer is option C. Mollusca.

Note:Arthropoda is the first largest phylum with 280000 species. They widely occur on land, in air and all sorts of water and many are a parasite on other organisms. Body of arthropods is covered by a chitinous exoskeleton. They have jointed appendages.