Given below is a diagram of an ecological pyramid of numbers. Choose the correct food chain from the list of food chains given, that represents the given pyramid.

The correct option is Grass → Rabbit → Fox → Flea.

Step-by-Step Explanation:
An ecological pyramid of numbers represents the number of individual organisms at each trophic level in a given ecosystem. Let us analyze the tiers of the pyramid shown in the diagram from the bottom to the top:

1. First Trophic Level (Base / Primary Producers):
The bottom-most bar is very wide, which indicates a large number of individual primary producers. In the correct food chain, this corresponds to Grass, which is highly abundant in a grassland ecosystem.

2. Second Trophic Level (Primary Consumers):
The second bar is narrower than the base, showing a decrease in the number of individuals. This represents the herbivores, which are Rabbits. The population of rabbits is smaller than the amount of grass available.

3. Third Trophic Level (Secondary Consumers):
The third bar is extremely narrow, indicating a very small number of individuals. This represents the carnivores, which are Foxes. There are only a few foxes supported by the rabbit population in the ecosystem.

4. Fourth Trophic Level (Tertiary Consumers / Parasites):
The top-most bar is wide again, which indicates a significantly larger number of individuals compared to the third trophic level. This represents parasites, specifically Fleas. A single host organism (such as a fox) can host hundreds of ectoparasites (fleas), leading to a huge increase in the number of individuals at this top tier.

Therefore, the partially inverted/spindle-shaped pyramid of numbers depicted in the image corresponds perfectly to the parasitic food chain: Grass → Rabbit → Fox → Flea.