What is a​ cross-sectional study? Choose the correct answer below. A. ​Cross-sectional studies are observational studies that are​ retrospective, meaning that they require individuals to look back in time or require the researcher to look at existing records. B. ​Cross-sectional studies are a list of all individuals in a population along with certain characteristics of each individual. C. ​Cross-sectional studies are observational studies that collect information about individuals at a specific point in time or over a very short period of time. D. ​Cross-sectional studies first identify a group of individuals to participate in the study. These individuals are then observed over a period of time. Over this period of​ time, characteristics about the individual are recorded