SAT Subject Biology Practice Question 87: Answer and Explanation

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Question: 87

17. Oxygen gas (O2) is produced by plants and algae. What is the source of oxygen atoms in these molecules?

A. Water
B. Glucose
C. Carbon dioxide
D. Atmospheric oxygen
E. Atmospheric nitrogen

Correct Answer: A


Water is the source of oxygen molecules released by the photosynthetic process, when water molecules are dissociated to free hydrogen ions.

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