A kind of variable that a researcher purposely changes in investigation is

What are igneous intrusions and extrusions

The human body stores chemical energy from digested food. some of the chemical energy is converted into mechanical energy when the body moves. which statement best supported by this information

15. one purpose of the tread pattern on a tire is to a reduce tire wear. b. reduce traction c. allow water to flow away from the tire. d. look impressive.