Question

which discovery supported the endosymbiotic theory?
dna in mitochondria
dna in the cell nucleus
dna in ribosomes
dna in the cytoplasm

Explanation:

The endosymbiotic theory proposes that mitochondria and chloroplasts were once free - living prokaryotes that were engulfed by a host cell. The presence of DNA in mitochondria supports this theory as it suggests that mitochondria have an independent genetic system, similar to prokaryotes. DNA in the cell nucleus is part of the eukaryotic cell's main genome and not relevant to the endosymbiotic origin of organelles. Ribosomes do not contain DNA. DNA in the cytoplasm is not a key discovery for the endosymbiotic theory in the same way as mitochondrial DNA.

Answer:

DNA in mitochondria