Determine What Type of Observational Study Is Described

Determine what type of observational study is described. Explain.
-Vitamin D is important for the metabolism of calcium and exposure to sunshine is an important source ofvitamin D. A researcher wanted to determine whether osteoperosis was associated with a lack of exposure tosunshine. He selected a sample of 250 women with osteoperosis and an equal number of women withoutosteoperosis. The two groups were matched - in other words they were similar in terms of age, diet,occupation, and exercise levels. Histories on exposure to sunshine over the previous twenty years wereobtained for all women. The total number of hours that each woman had been exposed to sunshine in theprevious twenty years was estimated. The amount of exposure to sunshine was compared for the two groups.

A) retrospective; Individuals are asked to look back in time
B) cross-sectional; Information is collected at a specific point in time.
C) cohort; Individuals are observed over a long period of time.