In a plant, what is formed by a group of xylem vessels? A. a cell
B. a tissue
C. an organ
D. an organ system

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

How is the motion of the particles of water at 80 ⁰c different from the motion of the particles of water when it is 30 ⁰c?

Which layer will become saturated first when rain falls?