Both originated in China.
Answer:
Living conditions in many of the city's tenements did endanger the health of residents. ... of the ideas that would influence the emerging field of public health. ... De Wolf's methods for preventing the spread of contagious disease ... of recently arrived Polish, Greek, Italian, and Eastern European families.
Explanation:
Contamination can have undesirable consequences in real experiments, some of them are related to the feelings that may arise in the research participants, the contamination bias reduces the differences between the research groups, and can cause a comparison between the treatments of each different group, the which can generate conflicts and rivalries on the part of groups that consider themselves to be inferior to others. These contamination-related problems can significantly interfere with the research results.
