How many chromosomes does a child inherit from his or her parents?
23 from the mother and 23 from the father
46 from the mother
46 from the father
46 from the mother and 46 from the father

Which of the following is a reason why early living organisms on earth could not have survived on the surface? 1. the lack of an ozone layer 2. the lack of oxygen in the atmosphere 3. the fact that these organisms were single-celled