The correct answer is D) a greater likelihood of the spread of disease.
In the late 19th century, poor hygiene, greater access to mass public transportation, and growing city population, all contributed to a greater likelihood of the spread of disease.
Overpopulation in some parts of large cities has increased the risk of spreading diseases for the immediate contact of people in corwed public spaces such as transportation, public buildings, and offices. Poor hygiene practices and sometimes lach of access to health services increased the risk of contagious of any diseases.