Step 1: Electron Microscopy Principle.
Electron microscopy, a high-resolution imaging method, necessitates a sufficient viral particle concentration in a sample for visible image generation.
Unlike light microscopy, electron microscopy relies on electron scattering, demanding a high viral load for adequate contrast formation.
Step 2: Minimum Required Concentration.
Approximately $10^{5}$ to $10^{6}$ particles per milliliter are needed for visualization.
Lower concentrations result in viral particles being too sparse for clear detection.
Step 3: Evaluation of Options.
- (A) $10$ to $10^{2}$ Particles/ml: Insufficient for visualization.
- (B) $10^{3}$ to $10^{4}$ Particles/ml: Below the necessary concentration.
- (C) $10^{5}$ to $10^{6}$ Particles/ml: Correct; this concentration range enables reliable visualization.
- (D) $10^{12}$ to $10^{16}$ Particles/ml: Excessively high and impractical concentration.
Step 4: Conclusion.
A minimum concentration of $10^{5}$ to $10^{6}$ particles/ml is required for virus visualization using electron microscopy.