Q.Pneumatic bones are seen in
a. Mammalia
b. Aves
c. Reptilia
d. Sponges

Step 1. Flight demands a light but strong skeleton, so birds evolved long bones that are hollow and contain air cavities, called pneumatic bones, connected to the respiratory air-sac system.

Step 2. The chapter specifically attributes pneumatic bones to Class Aves as part of its fully ossified but lightweight endoskeleton. …

Recall which vertebrate class the chapter specifically describes as having hollow …

• Confusing 'fully ossified' (true of birds) with 'solid, non-hollow' bones, when bird bones …