A Levels Biology (9700)•9700/12/M/J/23
Explanation
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
Topic: Infectious diseases
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