The deeper we go down in Earth's, crust, thewe go back in time (science)

The population of bacteria in a petri dish doubles every 40 seconds. the population of the bacteria is initially 400 organisms. what unit is most appropriate for the time at which the number of bacteria is 300? hour bacteria per hour second bacteria per second

Which layer will become saturated first when rain falls?

9. the history of life on earth is recorded in