Given a scientific question, generate a correct answer to it.
--------
Question: What two factors influence the pressure of fluids?

Answer: depth and density

Question: Carboxylic acids have an acidic hydrogen atom, but esters do not. what do esters have in place of an acidic hydrogen atom?

Answer: hydrocarbon group

Question: Energy from sunlight enters many ecosystems through what process?

Answer:
photosynthesis