According to the endosymbiotic theory, how did chloroplasts end up in producers’ cells?

• A. Producers inherited chloroplasts from viruses that integrated into the nucleus and later budded off as organelles
• B. An ancestral eukaryotic cell engulfed a photosynthetic prokaryote (such as a cyanobacterium) that survived and became a chloroplast
• C. Chloroplasts formed de novo from infoldings of the plasma membrane in early plant cells
• D. Chloroplasts evolved directly from mitochondria after mitochondria acquired chlorophyll-producing genes

Answer: (B)