I'd say heat, more specifically sunlight.
Why?
Because sun is the form of energy needed for plants to grow and live. Plants in turn are the form of energy needed for herbivores to live that later on turn out to be the form of energy needed by the carnivores. When these die, decomposers will be the ones to take advantage of the energy.
As you can see an ecosystem has already been formed: producers, secondary consumers, tertiary consumers or decomposers.
Hope it helped,
Happy homework/ study/ exam!
You can recognize the process of pinocytosis when THE CELL IS ENGULFING EXTRACELLULAR FLUID.
Pinocytosis is one of the forms of endocytosis; it involves the movement of large particle into the cell by an in-folding of the plasma membrane. It is an active form of transport used to move materials into the cells.
The answer is D) Sunlight.
Hope this helps!
-Payshence xoxo