Celery stalks that are immersed in fresh water for several hours become stiff and hard. similar stalks left in a salt solution become limp and soft. from this we can deduce that the cells of the celery stalk are

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