A survey of 7419 elementary school students in Tokyo, Japan asked questions regarding food education, screen time duration, obesity, physical activity, dry eyes, and learning ability. Researchers concluded children with shorter screen time durations presented with average body weight with an increase in grades and physical activity. What is the most likely design of this study?

a. Cross-sectional

b. Randomised controlled trial

c. Case-control

d. Prospective cohort