Why does each eon, era, period, or epoch not begin or end at a specific time?

According to the cell theory, which describes cells? a. all organisms are composed of multiple cells. b. all cells have the same structure and function. c. cells are found in everything on earth. d. living organisms are not created spontaneously

Which component in a graph indicates an independent factor? a. y-axis b. x-axis c. scale

What was the impact of the concordat of worms?