Question

Match the following:

• A. A-I, B-III, C-IV, D-II
• B. A-III, B-I, C-II, D-IV
• C. A-III, B-II, C-I, D-IV
• D. A-II, B-I, C-IV, D-III

Hint:

Placoid scales are modified teeth that are structurally homologous to vertebrate teeth.
They are a key diagnostic feature of all cartilaginous fishes.

Answer 1

The Correct Option is B

Step 1: Group each List-I structure by the animal class it belongs to.
Operculum and placoid scales point to fish, so sorting by vertebrate class before matching genus names makes the pairing much faster.
Step 2: Match the fish related structures.
Operculum, the bony gill cover, belongs to bony fish such as Labeo, giving A to III. Placoid scales, the tooth like skin scales, belong to cartilaginous fish such as Scoliodon, giving B to I.
Step 3: Match the remaining structures by elimination.
Working through the bird and mammal linked structures left in the list the same way, matching skeletal or muscular features to their representative genus, fills in C to II and D to IV.
Final answer: Option 2, A-III, B-I, C-II, D-IV.