Numerical answer
Five sentences related to a common theme are given below, labelled 1 to 5. Four of them can be sequenced into a coherent, meaningful paragraph; one does not fit. Identify the sentence that does not fit.
1. Vaccines work by training the immune system to recognise a pathogen before an actual infection occurs.
2. This training typically involves exposing the body to a weakened, inactivated, or partial version of the pathogen.
3. The immune system then produces antibodies and memory cells specific to that pathogen.
4. Malaria remains one of the leading causes of childhood mortality in sub-Saharan Africa.
5. If the real pathogen is later encountered, these memory cells allow a faster, stronger immune response.
1. Vaccines work by training the immune system to recognise a pathogen before an actual infection occurs.
2. This training typically involves exposing the body to a weakened, inactivated, or partial version of the pathogen.
3. The immune system then produces antibodies and memory cells specific to that pathogen.
4. Malaria remains one of the leading causes of childhood mortality in sub-Saharan Africa.
5. If the real pathogen is later encountered, these memory cells allow a faster, stronger immune response.
Show answer and solution
Answer: 4
Sentences 1, 2, 3 and 5 form a coherent explanation of how vaccines train the immune system, in logical sequence (mechanism → method → immune response produced → benefit on real exposure). Sentence 4 introduces an unrelated fact about malaria mortality that does not continue this explanatory chain, making it the odd one out.
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