A small standing crop of phytoplankton supports a large standing crop of zooplankton. This can be correctly represented by:

The correct option is Inverted pyramid of biomass.

To understand why this is correct, let us break down the concepts of ecological pyramids and biomass:
1. What is a Pyramid of Biomass?
An ecological pyramid of biomass shows the total dry weight of all living organisms (known as the standing crop) at each trophic level within an ecosystem at any given point in time. In most terrestrial ecosystems, this pyramid is upright because the biomass of the primary producers (such as grasses and trees) is much larger than the biomass of the herbivores and carnivores that depend on them.

2. Aquatic Ecosystem Dynamics
In aquatic ecosystems like oceans and deep lakes, the primary producers are phytoplankton. These microscopic organisms have extremely high rates of reproduction and very short lifespans. They grow and multiply rapidly, but they are also consumed by primary consumers (zooplankton) almost as fast as they are formed.

3. Standing Crop Comparison
Because the phytoplankton are consumed so rapidly, their standing crop (the biomass present at any single moment) remains very small. In contrast, zooplankton are larger, live longer, and consume vast quantities of phytoplankton, allowing them to maintain a larger standing crop of biomass at any given time. Consequently, a small standing crop of phytoplankton supports a larger standing crop of zooplankton.

4. The Inverted Shape
When we chart this distribution of biomass, the base level (producers) is much narrower than the level above it (consumers). This creates an upside-down or inverted pyramid of biomass.

Why the other options are incorrect:
- The pyramid of energy is always upright in every ecosystem because energy is continuously lost as heat at each trophic level during energy transfer. It can never be inverted.
- An upright pyramid of biomass would represent a system where producer biomass is greater than consumer biomass, which is the opposite of what is described here.