Vaccination programs are among the most cost-effective public health interventions available. Their success, however, depends not only on vaccine efficacy but on the logistical infrastructure that delivers doses to the populations who need them. In regions with weak distribution networks, even highly effective vaccines can fail to produce population- level protection.
Which choice best describes the function of the second sentence in the text?
- A
It supports the cost-effectiveness claim made in the first sentence.
- B
It defines the term 'vaccination'.
- C
It introduces an unrelated public health intervention.
- Dcheck_circle
It identifies the logistical condition that the cost-effectiveness claim presupposes.
Explanation
The second sentence specifies the logistical precondition for the headline claim. B captures this conditional function.