In the chain of infection for a respiratory pathogen, which sequence correctly orders the elements from source toward infection of a new host?

• A. Portal of entry → Transmission route → Reservoir → Portal of exit, which erroneously reverses the chain.
• B. Portal of exit → Reservoir → Portal of entry → Transmission route, which mixes the temporal order incorrectly.
• C. Transmission route → Portal of exit → Reservoir → Portal of entry, which does not reflect the directional flow of infection.
• D. Reservoir (infected host) → Portal of exit (respiratory secretions) → Transmission route (droplets/aerosols) → Portal of entry (susceptible host respiratory mucosa).

Answer: (D)