A newly developed composite dental filling material is hypothesized to reduce the occurrence of cold sensitivity of a restored tooth. Forty subjects each had two cavities that needed to be treated and each received two fillings. One tooth was restored with the new filling material and one tooth was restored with a leading brand of composite dental filling material. After 3 months, each tooth was sprayed with very cold water, and subjects rated whether they felt any or no sensitivity (yes or no) for each tooth. Which scenario below best describes the study design?

A. One group with one outcome (or variable of interest).

B. Two dependent or paired groups with one outcome

C. Two independent groups with one outcome

D. One group with two outcomes (or two variables of interest)