They would know if they see anything like traces of water or anything else that would be nessecary for a living organism to have. They look for these with technology like the hubble telescope as well as the drone on Mars to gather as much information as possible.
Answer:
glucose, energy, water, oxgen
Explanation:
Your answer would be A. The earth element stays in the same area of the lithosphere, hydrosphere, or atmosphere where they originated when the earth was formed.
Carbohydrates such as glucose, cellulose, deoxyribose, fructose, etc
Nucleic acids such as DNA, mRNA, tRNA
Proteins such as structural proteins and enzymes
Answer:
At the bottom you have the producers aka auto trophic livings (which use inorganic compounds to grow, produce energy, matter and so on..). These organisms would be plants, Cyrano bacteria, over all any organisms that do photosynthesis.