Producers, because they're the start of the food chain and without them there will be no food chain.
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a. radioactive isotopes. They use radioactive Phosphorus-32 as labels on a phage (bacteriophage) DNA that infects E. coli. Their experiment showed that the radioactive isotopes were only seen in E.coli and not in the phage.</span>
C. Plantae is the correct answer for you here
I believe the answer is glucose