The Reason That Deciduous Leaves Turn Red and Yellow in the Fall

The reason that deciduous leaves turn red and yellow in the fall is

A) Chlorophyll is converted into bright carotenoid pigments.
B) When chlorophyll breaks down,the red and yellow pigments which are already present become visible.
C) It is a chemical reaction involving the formation of ice crystals.
D) Bright pigments are shifted up from the roots while chlorophyll moves down.
E) Red and yellow pigments can only be made when temperatures are cool.