Annual Rings in a Tree Trunk Result from

Annual rings in a tree trunk result from

A) deposition of colored materials in the oldest cells.
B) the variation in cell size due to different growth conditions throughout a year.
C) the alternation of xylem and phloem produced in one year.
D) the kinds of cells,parenchyma or sclerenchyma,produced by the cambium.
E) the proportion of wood cells and cork cells in the xylem.