What is carbon useful for?

Which of the following was not a major animal on land during the carboniferous period? amphibians insects both a and b none of the above

What is the membrane that sheath of schwann cell containing cytoplasm and nucleus that encloses myelin

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