Final answer:
The correct answer is option B: age effects and cohort effects. Cross-sectional studies can be confounded by societal and cultural differences between cohorts that are not related to age, making it difficult to differentiate the true cause of observed variations.
Step-by-step explanation:
One problem with cross-sectional studies is the confounding of age effects and cohort effects. Cross-sectional research involves comparing multiple segments of the population at the same point in time. For example, a researcher might compare different age groups to assess their dietary habits, but differences between cohorts may reflect the distinct social and cultural experiences instead of actual age-related changes. Thus, option B, age effects and cohort effects, is the correct answer.
Such confounding occurs when the influences of two or more factors on an outcome cannot be distinguished. This makes it challenging to draw valid conclusions from such studies. For instance, the observed support for same-sex marriage between different age groups might reflect generational views rather than an actual shift in opinion as people age. In contrast, longitudinal research can better attribute changes over time directly to the participants' aging, rather than to cohort effects.