In the context of photosynthesis, the carbon that plants incorporate into sugars primarily comes from which source?

• A. Oxygen gas ($O_2$) released during photosynthesis
• B. Carbon dioxide ($C_0$$2$) in the atmosphere
• C. Organic carbon absorbed directly from the soil as glucose
• D. Carbon-containing minerals dissolved in groundwater

Answer: (B)

Verified step by step guidance

1. Understand that photosynthesis is the process by which plants convert light energy into chemical energy, producing sugars as a form of stored energy.
2. Recall that the general photosynthesis equation is: \$6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{light energy} \rightarrow C_6H_{12}O_6 + 6 \text{O}_2$.
3. Identify the source of carbon atoms in the sugar molecule \(C_6H_{12}O_6\) by looking at the reactants; carbon atoms come from carbon dioxide (\(\text{CO}_2\)) in the atmosphere.
4. Recognize that oxygen gas (\(\text{O}_2\)) is actually a product released during photosynthesis, not a source of carbon.
5. Conclude that plants incorporate carbon into sugars primarily from atmospheric carbon dioxide, not from organic carbon in soil or dissolved minerals.