From the observations, we can conclude that:
- Species X produces CO2 and H2O, which indicates that it is undergoing aerobic respiration (as aerobic respiration produces both water and carbon dioxide).
- Species Y produces ethyl alcohol and CO2, suggesting that it is undergoing fermentation, which is an anaerobic process since it does not use oxygen.
Based on this information, the correct conclusion is:
Only species Y is anaerobic.