Answer: Rough ER.
- A Smooth ER
- B Peroxisome
- C Lysosome
- D Rough ER
Correct answer: D. Rough ER
Explanation: Rough ER is studded with ribosomes that synthesise proteins for export, so protein-secreting cells are rich in it.
Animal cell structure with major organelles labeled. Image: LadyofHats (Mariana Ruiz), Public Domain, via Wikimedia Commons.
Concept context
Cell theory, prokaryotic vs eukaryotic cells, organelles and their functions. Foundation of all biology.