Air filter blocks airborne pathogens ≥1 μm

Steps:

• Determine transmission: HIV (blood), TB (airborne), malaria (mosquito), cholera (water/fecal-oral).
• Measure sizes: HIV virus (0.1 μm), TB bacteria (2-4 μm), malaria parasite (up to 10 μm but not airborne), cholera bacteria (1-3 μm but not airborne).
• Filter targets air system, so only airborne pathogens ≥1 μm are blocked.
• TB alone qualifies; others fail size or transmission criteria.

Why D is correct:

• D (x HIV, ✓ TB, x malaria, x cholera) matches: only TB is airborne and ≥1 μm.

Why the others are wrong:

• A incorrectly prevents malaria and cholera (not airborne).
• B prevents none, ignoring TB.
• C format unclear but implies all prevented (wrong).

Final answer: D