What is maximum in a pond-ecosystem?

The diagram shows a pyramid of numbers in a food chain. What type of organism is a caterpillar?

The given figure best represents:

The pyramid of numbers in a cropland ecosystem is:

Consider the following statements about ecological pyramids:
$I.$ Charles Elton developed the concept of ecological pyramid.
$II.$ After his name,these pyramids are also called as Eltonian pyramids.
$III.$ It is a graphical representation or pyramid-shaped diagram which depicts the number of organisms,biomass,and energy at each trophic level.
Which of the statements given above are correct?

What type of ecosystem is represented by the given ecological pyramid?