Answer:
Cross-sectional
Explanation:
Cross-sectional research: In psychological research, the term cross-sectional research is defined as one of the research methods in which the researcher or the experimenter uses different or distinct groups of participants that differ in the interest (variable) but share a few characteristics, for example, ethnicity, socioeconomic status, and educational background, etc. It has been widely used in the field of developmental psychology by various researchers.
In the question above, Karen is conducting cross-sectional research.