What causes blood pressure?
A. Cholesterol in the blood
B. Stress that exercises puts on heart muscles
C. Removal of oxygen from the blood
D. Contraction of the ventricles in the heart

Why are small quantities of chlorofluorocarbons so harmful to the ozone layer? a. the chlorofluorocarbons act like ultraviolet radiation causing large amount of ozone to be produced. b. the chlorine from the chlorofluorocarbons reacts with free molecules of oxygen causing a stop in ozone production c. free oxygen atoms can replace the chlorine in chlorine monoxide, releasing a free atom of chlorine which can then recombine with an oxygen atom in ozone, destroying more ozone. d. chlorofluorocarbons absorb ultraviolet radiation, preventing the formation of ozone select the best answer from the choices provided

Name the plastid and pigment likely to be found in the cells of (a) petals of sunflower (b) ripe tomato.

Use the drop down menus to match each example to the fossil topic discussed then to show how the fossil record gives evidence of evolution