CAIE A Level Biology 9700 · Infectious diseases
In a city, two districts were compared for tuberculosis (TB) incidence. District A has high population density, poorly ventilated shared accommodation, and limited access to healthcare. District B has lower density, well-ventilated housing, and good healthcare access. TB incidence is much higher in District A. Explain the biological and social factors that contribute to the spread of TB in crowded, poor conditions.
5 marks, so the mark scheme is looking for about 5 separate creditworthy points. Making the same point twice in different words earns it once.
Explain means: Give the reasons or the mechanism: why or how something happens. Link each point to the next with because, so or which means. A list of facts with no links usually loses the reasoning marks.
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