Question 4 of 10 Which two substances are needed for cellular respiration?
O A. Oxygen
O B. Sugar
O C. Water
D. Carbon dioxide

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

The smallest biological units that can evolve are

In the controversial scientific process of cloning, organisms are created that are genetically identical to there parent. this process would be classified as