Which material is a pure substance

What mistake did john needham make that caused him to conclude that spontaneous generation for microorganisms occurred? a. he re-contaminated his boiled broth solutions. b. he destroyed the vital force in the solutions. c. he did not boil his broth solutions, only warmed them. d. he failed to seal his flasks of boiled broth. e. he allowed his assistant to conduct the experiment which he did not monitor closely.

After frida stops exercising, she continues to breathe heavily. what is most likely occurring in her body? heavy breathing during exercise has produced an oxygen surplus in her muscles. this oxygen is being transported to her lungs. this is a result of aerobic respiration. heavy breathing during exercise has produced a carbon dioxide surplus in her muscles. lactate is being transported to her liver. this is a result of aerobic respiration. strenuous exercise has caused her body to be in carbon dioxide debt, and she is breathing hard while lactate is transported to the liver. this is a result of anaerobic respiration. strenuous exercise has caused her body to be in oxygen debt, and she is breathing hard while lactate is transported to the liver. this is a result of anaerobic respiration.

Why are some people more concerned about shark survival than about shark attacks?