Biology homework......Plz help!!!!!?

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mou

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1. What happens to blood as it passes through a kidney machine?
A. CO2 is removed
B. Glucose is added
C. Oxygen is added
D. Urea is removed

2. What causes the decrease in oxygen concentration in a lake polluted by sewage?
A. a decrease in the dissolved nitrate concentration.
B. a decrease in the number of consumers
C. an increase in the number of decomposers
D. an increase in the number of green plants

3. Which process doesn't result in the return of carbon dioxide to the atmosphere?
A. combustion of fossil fuels
B. decomposition of humus
C. photosynthesis by green plants
D. respiration by bacteria
 
1. The kidneys remove toxins from your body, such as urea and excess water, which helps make urine. The answer is D.
2. A decrease in consumers would increase oxygen due to less being taken in for respiration. An increase in green plants would increase oxygen due to less being removed from photosynthesis. An increase in decomposers would decrease oxygen due to more being taken in due for respiration. C
3. Combustion of fossil fuels adds CO2 to the atmosphere, along with respiration and decomposition. Photosynthesis, however, takes in CO2 in the atmosphere. C
 
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