CAIE A Level Biology 9700 · Infectious diseases
In a densely populated urban slum, the incidence of tuberculosis (TB) is very high. The housing is cramped, windowless, and poorly ventilated. Most residents have a diet low in protein and vitamins, and access to healthcare is limited. Explain why these conditions favour the spread and persistence of TB in this population.
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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