The correct answer is (d) 5000 kJ.
Explanation:
In a food chain, only about 10% of the energy at each trophic level is transferred to the next level.
Since the energy at the fourth trophic level (Hawk) is 5 kJ, this means that at the third trophic level (Snake), there must have been 50 kJ (5 kJ * 10).
At the second trophic level (Frog), there would have been 500 kJ (50 kJ * 10).
And at the first trophic level (Grasshopper), there would have been 5000 kJ (500 kJ * 10).
Therefore, the energy available at the producer level (Grass) is 5000 kJ.