When an organic compost pile is built correctly (sufficiently large, slightly moist, and containing a variety of organic material), it tends to get hot. which of the following best explains why a compost pile gets hot? solar energy hitting the pile causes photosynthetic microorganisms in the pile to begin working and releasing the stored energy as heat. water molecules within the compost pile spontaneously break down and release their energy as heat. the decomposers are breaking down energy-containing organic molecules for their own use and some of the energy escapes as heat. the decomposers are constantly moving around within the compost pile and the friction of their motion heats up the pile.