Final answer:
Lynn Margulis's proposal of the endosymbiotic theory, explaining the origin of mitochondria and chloroplasts from prokaryotic cells. The correct answer is option c).
Step-by-step explanation:
The proposal of the endosymbiotic theory of mitochondrial and chloroplast origin that was ultimately accepted by the greater scientific community was made by Lynn Margulis. Margulis, an American geneticist, published her ideas regarding the endosymbiotic hypothesis of the origins of mitochondria and chloroplasts in 1967.
She presented a growing body of evidence, including microscopic, genetic, molecular biology, fossil, and geological data to support her claims that eukaryotic organelles such as mitochondria and chloroplasts are of prokaryotic origin.
Initially met with resistance, Margulis's endosymbiotic theory eventually gained wide acceptance as more evidence became available, particularly through advances in DNA sequencing which confirmed the similarities between mitochondrial and chloroplast DNA and their bacterial counterparts.