Didn't know what other category to ask this in. How does soil form differently in different parts of the world and what impact does it have on living things? What factors affect soil formation and loss?

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