Does the rate of cellular respiration increase or decrease if oxygen is removed from the air

What happens when a scientific theory is shown to be an accurate description of a phenomenon?

Which of the following molecules could pass through the plasma membrane by simple diffusion? a. na+ ions b. glucose c. amino acids d. carbon dioxide

How have crops been modified? a.plants have been made more susceptible to pests b.plants have been made resistant to herbicides c.plants have been made more susceptible to herbicides d.plants have been modified to have reduced yield