Answer to Question 1
1. Filoplume
2. Down
3. Contour, or flight, feathers
4. Powder down
Answer to Question 2
(a) Hollow bones
(b) Air sacs within the wings and body
(c) Sternum (keel bone)
(d) Fused ribs for stability
(e) Strong pectoral muscles attached to the wings
(f) Feathers