Final answer:
The slug is the correct answer to the question about which of the following is a mollusk. Slugs belong to the phylum Mollusca, which encompasses a diverse array of mostly marine species, including terrestrial mollusks such as slugs that have common features like a mantle and a radula.
Step-by-step explanation:
The correct answer to the question 'Which of the following is a mollusk?' is d) slug. The phylum Mollusca is a diverse group of mostly marine invertebrates, and slugs are terrestrial mollusks. They share common characteristics with other mollusks, such as a mantle that can secrete a calcareous shell in many species and a radula, which is a rasping feeding organ present in most mollusks.
The other options provided in the question do not belong to the phylum Mollusca: a mit is an arachnid, a nematode belongs to the phylum Nematoda, a scallop is correctly identified as a mollusk (specifically a bivalve), but it is not the answer provided by the student, and microplasma is incorrect as it is actually 'Mycoplasma', a genus of bacteria.
A mollusk is a type of invertebrate animal belonging to the phylum Mollusca. They are a diverse group of organisms that can be found in marine, freshwater, and terrestrial habitats. Mollusks are characterized by their soft bodies, muscular foot, and usually a protective shell. Examples of mollusks include snails, clams, squid, and octopuses.