D. 90%
Step-by-step explanation:
- When energy flows in a food chain, it is observed that the amount of energy flow decreases with successive trophic levels.
- It is generally observed that approximately 90% of the energy available at a trophic level is used up and only remaining 10 % is transferred to the next .
- This is termed as ten percent law.
- Thus, we can say that 90% of energy is lost when the energy is transferred from one trophic level to another.