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.

- "ethical issues. deception – the participants actually believed they were shocking a real person and were unaware the learner was a confederate of milgram's. however, milgram argued that “illusion is used when necessary in order to set the stage for the revelation of certain difficult-to-get-at-truths.” "

- "milgram's work was conducted in the early 1960s before the current.the studies ignited a debate about the ethical treatment of participants. what appear to be dangerous, if not deadly, electric shocks and the by today's ethical standards, many questions about the research have gone unanswered."

answer; i believe the correct answer is prefrontal cortex;