Question

question 4
autotrophs use ______________ as their organic source.
o2
co2
h2o

Explanation:

Autotrophs, like plants, perform photosynthesis. They use carbon - dioxide ($CO_2$) from the atmosphere and convert it into organic compounds such as glucose through the process of photosynthesis. Oxygen ($O_2$) is a by - product of photosynthesis and water ($H_2O$) provides electrons and hydrogen ions but not the carbon for organic compounds.

Answer:

B. CO2