They were hindered by economic development and lack of enforcement, so I'd say 1. Cost, because no one would pay for it.
The correct answer is A. There are more rats than people in our town these days.
Explanation
The Black Death was the most devastating pandemic in human history, affecting Europe and parts of Asia during the 14th century. The main reason why this disease spread quickly was due to the increase of rats throughout Europe, because the disease was transmitted by the bite of rat fleas. Therefore, the sentence of the fragment that illustrates the real cause of the plague is A. There are more rats than people in our town these days.
The founder of communist ideology was Karl Marx.
The theory of communism was advanced by Vladimir Lenin.
