Step 1: Transmission Modes of Infectious Diseases.
Infectious diseases can spread through various means:
- Airborne transmission: Diseases like flu, tuberculosis, and COVID-19 spread through respiratory droplets or aerosols.
- Waterborne transmission: Diseases like cholera and typhoid spread through contaminated water.
- Contact transmission: Diseases like the common cold and skin infections spread through direct physical contact or contact with contaminated surfaces.
Step 2: Why Other Options are Incorrect.
- (A) Air: While many diseases do spread through the air, it is not the only mode of transmission.
- (B) Water: Some diseases are transmitted through water, but others spread by different means.
- (C) Contact: Contact transmission is only one form of disease spread, not the only one.
Step 3: Conclusion.
Infectious diseases can spread through multiple modes, so the correct answer is (D) All of these.