Question

multiple choice question
the oxygen produced during photosynthesis comes from
carbon dioxide split by an enzyme.
a water molecule split by energy from the sun.
a water molecule split by an enzyme.
carbon dioxide split by the energy of the sun.

Explanation:

In photosynthesis, the light - dependent reactions involve the splitting of water molecules ($\ce{H_2O}$). The energy from the sun (light energy) is used to split water into oxygen, protons, and electrons. Carbon dioxide is used in the Calvin cycle (light - independent reactions) to form glucose and is not the source of the oxygen produced. Also, the splitting of water in photosynthesis is driven by light energy, not an enzyme. So the oxygen produced during photosynthesis comes from a water molecule split by energy from the sun.

Answer:

B. a water molecule split by energy from the sun (assuming the options are labeled A, B, C, D with the second option being B as per the order: first option "carbon dioxide split by an enzyme", second "a water molecule split by energy from the sun", third "a water molecule split by an enzyme", fourth "carbon dioxide split by the energy of the sun")