The answer is; a) they are naturally occurring.
Answer:
An autotroph is a cell that is capable of producing its own energy using photosynthesis or, less commonly, chemosynthesis.
A heterotroph is a cell that must consume its energy from external sources, for instance, hunting for prey or eating autotrophs.
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Answer:
Why is aerogel blue? The sky, glaciers and aerogel all have tiny particles or bubbles that scatter light.
Explanation:
