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.
Answer:
B. breaches in the poorly-designed levees
Explanation:
In case of not considering hurricane Katrina a natural disaster, a series of human errors would be highlighted, such as the neglect of a fragile embankment constructed to prevent the overflow of a river.
The rest of the options are incorrect because they all describe natural hazards like strong winds, heavy rain and flooding produced by a sudden, powerful storm.
