3. what causes blood pressure?
a. cholesterol in the blood
b. stress that exercise puts on heart muscle
c. contraction of the ventricles in the heart
d. removal of oxygen from the blood

The shift of a vehicle's weight around its center of gravity is known as

Which of these is true for bacteria because they are prokaryotic cells? a. they can engulf body cells in order to make memory cells. b. they must invade viruses in order to reproduce. c. they are much larger than eukaryotic body cells. d. they can reproduce on their own outside of other cells.

Ascientific idea becomes valid when it is what?