What are some key elements when discussing the rotation and revolution of the Moon and Earth?

Which of the following produces carbon dioxide? a. plants b. animals c. decomposers d. all of the above

Which of these substances does not protect against invaders in the nonspecific immune response? a. saliva b. mucus c. tears d. urine

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