Humans convert approximately ________ of the energy stored in food to useful work.55%99.9%34%22%

To answer the question regarding the percentage of energy stored in food that humans convert to useful work, let's analyze the options provided:

1. 55% - This figure could be plausible given the general efficiency of human metabolic processes.
2. 99.9% - This option seems excessively high, as biological systems typically do not achieve such efficiency.
3. 34% - While relatively low, it may be representative of a specific context or dataset but is less commonly cited.
4. 22% - This figure is more reflective of estimates found in various biological and energy studies regarding human metabolism.

Analysis and Conclusion

The most widely accepted estimate for the efficiency of energy conversion in humans suggests that about 20% to 30% of the energy from food is converted into useful work, with some studies indicating about 25% as a more accurate figure. Therefore, out of the options provided, 22% seems to be the closest to the general consensus regarding the conversion efficiency of energy in humans.

Final Answer

22%