Question

1. Secondary endosymbiosis refers to
   1. Endosymbiosis of a prokaryote by a eukaryote
   2. Endosymbiosis of chloroplasts since primary endosymbiosis created mitochondria
   3. Endosymbiosis of a photosynthetic eukaryote by another eukaryote
   4. Endosymbiosis that has a minor impact relative primary endosymbiosis
   5. The colonization of land by the earliest land plants

Answer 1

Secondary symbiosis is the process that eukaryotic cells engulfing another eukaryotic cell which was already undergone an endosymbiosis. so answer from the options is C) endosymbiosis of a photosynthetic eukaryote by another eukaryote

photosynthetic eukaryote has chloroplast which it acquires through endosymbiosis.