An experiment is conducted to track the pathway of oxygen atoms during photosynthesis. A culture of the green alga Chlorella is supplied with carbon dioxide containing the heavy oxygen isotope 18O^{18}\text{O}18O (in the form of C18O2\text{C}^{18}\text{O}_2C18O2) and water containing the standard oxygen isotope 16O^{16}\text{O}16O (in the form of H216O\text{H}_2^{16}\text{O}H216O).
Which of the following correctly identifies the isotopic composition of the oxygen gas and glucose produced by the algae?
Oxygen gas contains 18O^{18}\text{O}18O only; glucose contains 16O^{16}\text{O}16O only.
Oxygen gas contains 18O^{18}\text{O}18O only; glucose contains 18O^{18}\text{O}18O only.
Oxygen gas contains 16O^{16}\text{O}16O only; glucose contains 18O^{18}\text{O}18O only.
Oxygen gas contains 16O^{16}\text{O}16O only; glucose contains 16O^{16}\text{O}16O only.
