Which of the Following Describes a Risk Associated with Cross-Sectional

Which of the following describes a risk associated with cross-sectional research on IQ?

A) In a cross-sectional study that compares IQ scores,the difference in IQ scores of 25-year-olds and 45-year-olds is due to differences in educational attainment.
B) In a cross-sectional study that compares IQ scores,the difference in IQ scores of 25-year-olds and 45-year-olds is due to the 45-year-olds having taken the same test at several points in time.
C) In a cross-sectional study,the participants may move or die before the study has been completed.
D) In a cross-sectional study,the researchers incur significant expenditure of time as he or she waits for the participants to get older.