I believe the answer is A!
If you change two of the three variables than you don’t know if the change is caused by variable A or variable B. In this case if you keep light constant but change the amount of co2 and the color of the light, you can’t which of these two are affecting photosynthesis.
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Answer:
the part is the esophagus
Explanation:
due to the akalied water entering to fast. hopefully this helps.