Visibility of cellular structures under light microscopy

Steps:

• Light microscopes resolve structures larger than 0.2 μm with 400x magnification and staining.
• Daylight provides visible wavelengths (400-700 nm), limiting resolution to ~200 nm.
• Staining enhances contrast for larger organelles in plant cells.
• Compare structure sizes: nucleoli (2-5 μm) vs. smaller components like grana or ribosomes.

Why C is correct:

• Nucleoli are dense RNA-protein aggregates (1-8 μm) that stain prominently with basic dyes, exceeding light microscope resolution limits.

Why the others are wrong:

• A: Chloroplast grana are stacked thylakoids (~0.3-0.5 μm thick), below resolution without electron microscopy.
• B: Lysosomes are small vesicles (~0.1-1 μm), often obscured in plant cells and require advanced staining.
• D: Ribosomes are ~20-30 nm particles, far smaller than the 0.2 μm diffraction limit.

Final answer: C