Which of the following options will replace the question mark (?)?
Octopus : Mollusca :: Spider : ?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Arthropoda
The pair links an animal with the phylum (major animal group) it belongs to. The octopus is a soft-bodied animal of the phylum Mollusca. The spider has jointed legs and a hard outer covering, so it belongs to the phylum Arthropoda, the group that also includes insects and crabs.
Why the other options are incorrect
Option (2) Clean — Incorrect. This is a describing word, not an animal group.
Option (3) Web — Incorrect. A web is what a spider spins, not the group it belongs to.
Option (4) Genus — Incorrect. Genus is the name of a level of classification, not the name of a particular group like Mollusca.