Match the following concrete example to the correct sequence of chain-of-infection steps: A COVID-infected person in a household sneezes; virus-laden droplets land on a doorknob; a roommate touches the doorknob and rubs their eye and later becomes colonized in the nasal mucosa. Which ordered sequence fits this scenario?

• A. Reservoir (infected person) → Portal of exit (gastrointestinal shedding) → Transmission (vector-borne via insect bite) → Portal of entry (ear) → Colonization (bloodstream)
• B. Reservoir (infected person) → Portal of exit (nose/mouth via sneeze) → Transmission (fomite on doorknob) → Portal of entry (eye then nose) → Colonization (nasal mucosa)
• C. Reservoir (environmental soil) → Portal of exit (unknown) → Transmission (direct contact only) → Portal of entry (mouth) → Colonization (cutaneous surface)
• D. Reservoir (doorknob) → Portal of exit (hand) → Transmission (airborne droplet long-range spread) → Portal of entry (skin) → Colonization (intestinal tract)

Answer: (B)