Help please I’m confuse

What role do bacteria play in the carbon cycle

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

Which of the following molecules could pass through the plasma membrane by simple diffusion? a. na+ ions b. glucose c. amino acids d. carbon dioxide