The detail which doesn't support the central idea is, "Government leaders, who worked in a building beside the Thames, were seen fleeing with tears streaming
from their eyes." (p. 18)
Answer: Option C.
Explanation:
The central idea of any text is its main idea which ties all the other elements in the text together. The central idea mentioned here is about sanitation, and unsafe sanitation resulted in health issues in London. The first two sentences clearly supports the central idea.
The first sentence shows how thousands of people have died due to polluted water of river Thames. Second sentence also describes how cholera epidemics which is a bacterial disease that spread in water have taken life of around 30,000 people. Third sentence on the other hand doesn't support central idea since there isn't any mention of health problem in the sentence.