Question

why do scientists believe the mitochondria and chloroplasts were once independent cells? they have similar dna to prokaryotes. they copied the dna of the host cell. they are identical dna to host cells.

Explanation:

The endosymbiotic theory explains that mitochondria and chloroplasts were once independent prokaryotic cells. Key evidence is their DNA: it's circular (like prokaryotes) and similar to prokaryotic DNA, not matching host (eukaryotic) DNA. The first option states they have similar DNA to prokaryotes, which aligns with the theory. The second is wrong (they don't copy host DNA) and the third is wrong (their DNA isn't identical to host cells).

Answer:

A. They have similar DNA to prokaryotes.