How do rocks, fossils, rock layers, and Earths processes help to determine the age and geologic history of the Earth?

To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events.

it has one origin of replication, but it proceeds in two directions - d)

it is called the mitotic spindle