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:

Mitochondria and chloroplasts have circular DNA, similar to prokaryotes. This supports the endosymbiotic theory that they were once independent cells. Host - cell DNA is linear (in eukaryotes), so options about copying host - cell DNA or being identical to host - cell DNA are incorrect.

Answer:

They have similar DNA to prokaryotes.