What is the main difference between cross-sectional and longitudinal surveys? Group of answer choices Cross-sectional surveys are administered at a single point in time, while longitudinal surveys have follow-up surveys Longitudinal surveys are administered at a single point in time, while cross-sectional surveys have follow-up surveys Cross-sectional surveys are administered with follow-up surveys, while longitudinal surveys are not Longitudinal surveys are administered with follow-up surveys, while cross-sectional surveys are not