The correct answer is d) the carbon in carbon dioxide is recycled during photosynthesis.
During photosynthesis, plants absorb carbon dioxide (CO₂) from the atmosphere. Through a series of reactions involving sunlight, water, and nutrients, they convert this carbon dioxide into glucose (a form of sugar), which serves as energy and building material for the plant. The process of photosynthesis can be summarized by the overall equation:
\[ 6 , CO_2 + 6 , H_2O + \text{light energy} \rightarrow C_6H_{12}O_6 + 6 , O_2 \]
In this equation, carbon from carbon dioxide is incorporated into glucose and oxygen is released as a byproduct. Thus, plants effectively recycle carbon through the process of photosynthesis.