Like longitudinal research, cross-sectional studies can be threatened by

 The correct answer is :  cohort effects

Explanation:  The cohort study is a kind of analytical research and with observation, where a comparison is made of the frequency of occurrence of an event between two groups, one group is exposed to a factor that is not present in the other group. In a cohort study the research can be prospective or retrospective.

"social stratification refers to the way people are ranked and ordered in society. in western societies, stratification is primarily seen and understood as a result of socioeconomic status, which produces a hierarchy in which access to resources, and possession of them, increases from the lower to the upper strata"

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