How many carbon atoms combine in the photosynthesis reaction?(1 point)

In the photosynthesis reaction, six carbon atoms combine. The overall equation for photosynthesis can be represented as:

\[ 6 \, CO_2 + 6 \, H_2O \rightarrow C_6H_{12}O_6 + 6 \, O_2 \]

This shows that six molecules of carbon dioxide (each containing one carbon atom) are used to produce one glucose molecule, which contains six carbon atoms. Therefore, the correct answer is:

**6**