The common cold, hepatitis, and measles are examples of:

• A. Protozoan diseases
• B. Bacterial diseases
• C. Fungal infections
• D. Viral diseases

Answer: (D)

Verified step by step guidance

1. Identify the nature of the diseases listed: common cold, hepatitis, and measles are all caused by viruses, not by protozoa, bacteria, or fungi.
2. Recall the classification of infectious agents: Protozoa are single-celled eukaryotes, bacteria are prokaryotic microorganisms, fungi are eukaryotic organisms like molds and yeasts, and viruses are acellular entities that require host cells to replicate.
3. Understand that viral diseases are caused by viruses, which are responsible for illnesses such as the common cold (caused by rhinoviruses), hepatitis (caused by various hepatitis viruses), and measles (caused by the measles virus).
4. Eliminate the incorrect options by matching the causative agents: since these diseases are not caused by protozoa, bacteria, or fungi, those options can be ruled out.
5. Conclude that the correct classification for these diseases is 'Viral diseases' because their causative agents are viruses.