What is a major disadvantage of cross-sectional research?

One major disadvantage of cross-sectional research is that factors affecting individual development cannot be explored thoroughly. Cross-sectional research involves comparing different groups of people at one specific point in time, and does not allow for tracking individual changes over time. This limitation means that the unique influences and trajectories of individual development may be overlooked in cross-sectional studies. Choices A, B, and D are incorrect. Choice A is not a major disadvantage of cross-sectional research as age-related changes can still be compared across different groups in this type of study. Choice B, while a potential issue in any study, is not specific to cross-sectional research. Choice D refers to a different type of bias caused by repeated testing rather than a major disadvantage of cross-sectional research.