How many years did the precambrian era span? 2.5 billion 5 million 5,000 none of the above

Which factor that affects biodiversity?

To test the responsiveness of the kidneys, scientists have designed an experiment tracking urine output of people during a normal day, while regulating the in-take of water by mouth. what would be an appropriate hypothesis for this experiment?

Which pair of chromosomes determines sex in humans? a.15th b.1st c.23rd