The most abundant elements in the body are hydrogen, oxygen, carbon, and what?

Which of the following is a common danger of commercial fishing?

Which units ate used to measure both velocity and speed? check all that apply

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