Which of the following statements are true A calorie is a unit of heat
B one calorie is the energy required to raise 1 kilogram of water
C the preferred unit in metabolism studies and nutrition label is a kilogram

Why do leaves change color in the fall? green pigments break down and no longer mask the color of chlorophyll. chlorophyll breaks down and no longer masks the colors of other pigments. red- and yellow-colored pigments grow and mask green-colored chlorophyll. green-colored chlorophyll breaks down and turns red and yellow.