Which of the Following Best Addresses the Nature of the Threat

Multiple Choice

Which of the following best addresses the nature of the threat to internal validity that is caused by attrition?

A) changes in how a variable is measured during the course of the study
B) the differential dropping out of the participants from a study
C) an unexpected or unrelated event occurring during the study that could influence responses
D) physiological changes occurring in participants during the course of the study