Answer:
longitudinal
Explanation:
Longitudinal study is a research method that aims to analyze variations in the characteristics of the same sampling elements (individuals, companies, organizations, etc.) over a long period of time - often several years. An example of this happens when a researcher is interested in learning how children's moral development changes between the ages of three and five, to assess this development the researcher decides to follow them up to five years, periodically testing them over the years.
The first defense against a contagious disease is :
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