Visibility of cellular structures under light microscopy

Steps:

• Light microscopes resolve structures down to 0.2 μm at 400x magnification with staining.
• Compare structure sizes: nucleoli (1-5 μm) exceed resolution limit; grana (<0.1 μm), lysosomes (0.2-0.5 μm in plants), ribosomes (0.02 μm) do not.
• Staining enhances contrast for larger organelles like nucleoli in the nucleus.
• Daylight limits advanced techniques, relying on basic resolution for visibility.

Why C is correct:

• Nucleoli are dense RNA-protein aggregates (1-5 μm) that stain prominently with basic dyes, making them resolvable per Abbe's diffraction limit (d = λ / 2NA, ~0.2 μm for visible light).

Why the others are wrong:

• A: Grana are sub-micrometer thylakoid stacks, below resolution even with staining.
• B: Plant lysosomes (vacuolar) are small (0.2-0.5 μm) and lack distinct staining visibility at 400x.
• D: Ribosomes are 20-30 nm, 10x smaller than resolution limit.

Final answer: C