What observation led researchers to propose that chloroplasts evolved from cyanobacteria? A) Both produce proteins. B) Both contain mitochondria. C) Both provide structure to cells. D) Both perform photosynthesis.

I think the correct answer from the choices listed above is option D. Researchers were led to propose that chloroplasts evolved from cyanobacteria because they observed that both of them perform photosynthesis. Hope this answers the question.