What are the parts of the cell theory? (choose all that apply)." A. Most living things are made of about 50% cells

B. All cells come from preexisting cells

C. Cells are composed of tiny parts called organelles

D. All organisms are composed of one or more cells

E. The cell is the basic unit of organization

F. Cells can arise spontaneously

G. Cells are only visible through a microscope,