The correct answer is<u><em> B) multiple outbreaks of cholera</em></u>
Explanation:
Before the sewage crises, also known as the 'Big Stink', London had experienced over 3 outbreaks of Cholera. However, this not a contributing factor to the crises but actually a 'cause'
The rest of the options were in fact, contributing to the overburdened sewerage system. London's population had increased from just one million to over 3 million within a 100 years the infrastructure was old and failing.
Flushing toilets were introduced a couple of decades ago and significantly increased the amount of waste water handled by the sewerage system every day.
