Answer:
is about 4.6 billion years old
Answer:
Cellular differentiation is the process in which a cell changes from one cell type to another. Usually, the cell changes to a more specialized type. Differentiation occurs numerous times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types.
Im pretty sure that it is (A) because blood pumps to get every where through your body. If it didn't one half of your body would feel cold or numb.
