Hewo random peps ;-; I ish back with more questions so heres what I think the answers are. 1. A C or D 2. C or D 3. A 4. A or D

Abird flies by moving its wings up and down. which two systems are most directly responsible for the movement of a bird's wings? a. skeletal and muscular systems b. respiratory and muscular systems c. skeletal and digestive systems d. respiratory and digestive systems