Hint: A pyramid of numbers represents the number of individual organisms at each trophic level of the food-chain in an ecosystem. An ecosystem which contains less number of producers is represented by an inverted pyramid.
The pyramid of numbers shows the number of organisms at each trophic level in a food chain. A large number of insects feed upon a very big tree. These insects are eaten by the small birds. The small birds are further eaten by large birds.
According to the question, the number of insects is greater than the number of trees and the birds. So the correct sequence is represented as C>D>B>A.
The incorrect sequence is D>A>B
Ecological pyramids are of different types-
A. Pyramid of number- it represents relationships in terms of numbers between producers and consumers within the ecosystem
B. Pyramid of biomass- it represents the relationship between producers and consumers in terms of biomass.
C. Pyramid of energy –It represents the relationship between producers and consumers in terms of flow of energy within an ecosystem.
Hence, the correct answer is option (B)
Note: In an upright pyramid of numbers, the organisms decrease from the base to the tip. The upright pyramid is found in the grassland ecosystem where the producer or the grass is abundant than the consumers. Pyramid of energy can never be inverted.