Question

multiple choice question
it is hypothesized that chloroplasts were once ______.

• indistinguishable from mitochondria
• hydrogenosomes
• nonphotosynthetic
• free - living bacterial cells

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Explanation:

This is based on the endosymbiotic theory, which states that chloroplasts originated from free-living photosynthetic bacteria (cyanobacteria) that were engulfed by a larger eukaryotic cell and evolved into the organelles we see today. The other options are incorrect: chloroplasts are distinct from mitochondria/hydrogenosomes, and chloroplasts are specialized for photosynthesis so they are not nonphotosynthetic.

Answer:

free-living bacterial cells